Level control systems for high purity chemical delivery systems

ABSTRACT

A highly reliable digital level sensor assembly is provided to replace optical and capacitance type sensors in high purity chemical delivery systems. The digital level sensor assembly is particularly useful in bulk chemical refill delivery systems for high purity chemicals employing a manifold that ensures contamination free operation and canister change outs with a minimum of valves and tubing.

This is a continuation of U.S. application Ser. No. 08/485,968 filedJun. 7, 1995, now U.S. Pat. No. 5,711,354, which is a continuation ofU.S. application Ser. No. 08/345,244 filed Nov. 28, 1994, now U.S. Pat.No. 5,607,002, which is a continuation-in-part of U.S. application Ser.No. 08/184,226 filed Jan. 19, 1994, now abandoned, which is acontinuation-in-part of Ser. No. 08/054,597, filed Apr. 28, 1993, nowU.S. Pat. No. 5,465,766.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention relates to chemical delivery systems, inparticular containers, manifolds and level sensing schemes for chemicaldelivery systems.

2. Description of Related Art

The chemicals used in the fabrication of integrated circuits must have aultrahigh purity to allow satisfactory process yields. As integratedcircuits have decreased in size, there has been a directly proportionalincrease in the need for maintaining the purity of source chemicals.This is because contaminants are more likely to deleteriously affect theelectrical properties of integrated circuits as line spacing andinterlayer dielectric thicknesses decrease.

One ultrahigh purity chemical used in the fabrication of integratedcircuits is tetraethylorthosilcate (TEOS). The chemical formula for TEOSis (C₃H₅O)₄Si. TEOS has been widely used in integrated circuitmanufacturing operations such as chemical vapor deposition (CVD) to formsilicon dioxide films. These conformal films are generated upon themolecular decomposition of TEOS at elevated temperatures and reducedpressures (LPCVD), or at lower temperatures in plasma enhanced andatmospheric pressure reactors (PECVD, APCVD). TEOS is typically used forundoped, and phosphorous and boron doped interlayer dielectrics,intermetal dielectrics, sidewall spacers and trench fillingapplications.

Integrated circuit fabricators typically require TEOS with 99.999999+%(8-9's+%) purity with respect to trace metals. Overall, the TEOS mustexhibit a 99.99+% purity. This high degree of purity is necessary tomaintain satisfactory process yields. However, it also necessitates theuse of special equipment to contain and deliver the high purity TEOS tothe CVD reaction chamber.

Traditionally, high purity TEOS (and dopants) has been fed to the CVDreaction chamber from a small volume container called, an ampule.Historically, it was strongly believed ampules could not be metallic andthat no metal should interface with the high purity TEOS or other sourcechemicals in the ampule. The use of metal ampules are spurned in theindustry on the basis of the belief that high purity TEOS and other highpurity source chemicals used in the semiconductor fabrication industrywould pick up contamination from the metallic container in the form ofdissolved metal ions. Thus, the industry used, almost exclusively,quartz ampules.

When these relatively small quartz ampules were emptied, they wouldsimply be replaced with a full ampule. The ampules were not refilled inthe fabrication area. The empty ampule was returned to the chemicalmanufacturer who would clean and refill the ampule.

Inconveniences resulting from the use of the quartz ampules are thatthey require frequent replacement due to their small size, whichincreases the potential for equipment damage. Furthermore, quartzampules are subject to breakage, and have limited design versatility.Also, quartz has limited heat capacity making it difficult to controltemperature of the ampule. Plus, the lack of effectivequartz-to-stainless steel seals created significant leak problems.

In an attempt to solve the problem associated with quartz ampules, atleast one supplier of ultrahigh purity chemicals, Advanced Delivery &Chemical Systems, Inc., going against the belief in the industry thathigh purity source chemicals should not be placed in contact with metal,developed a stainless steel ampule. This ampule was used to directlysupply high purity TEOS and other high purity source chemicals tosemiconductor fabrication equipment. As with the quartz ampules, when itwas empty it was not refilled, but rather returned to the supplier forcleaning and refilling.

There were still several problems with using the stainless steel ampule.Namely, because of the small size of the these ampules, they oftenrequired frequency replacement. Also, an optical sensor employing aquartz rod was used to detect when the high purity TEOS reached a lowlevel inside the ampule. Unfortunately, optical sensors, which employ alight emitting diode and a photodetector in combination with a quartzrod, require a high degree of maintenance because they are subject tomisalignment if jostled. Furthermore, the conditioning circuit of thesensor must be constantly tuned because the sensor is subject tocalibration drift, which can cause false sensor output signals. Theseproblems can result in allowing the ampule to run dry or causing thepremature removal of a partial or full ampule. Another problem withoptical sensors is that they are prone to breakage in transport andcleaning, requiring frequent replacement. Despite these problems,optical sensors were used over more reliable metallic float sensorsystems because of the fears of contaminating the high purity chemicalwith metal particles and metal ions.

In an attempt to solve the problem of frequent replacement of stainlesssteel ampules, a larger five gallon stainless steel tank was developedto refill the smaller stainless steel ampule. This tank also used anoptical level sensor to detect when the container had been depleted,despite all of the problems associated with optical level sensors. Likethe ampule in the previous configuration, this tank was not refilled,but was rather returned to the supplier for cleaning and refilling. Dueto the size and weight of the five-gallon tank, it is subject to morephysical jarring than the smaller ampules when transported and changedout with empty canisters, thus causing a higher frequency of problemswith the traditional optical sensors used to detect a low level ofsource chemical in the delivery system.

Furthermore, in this refill configuration a second optical sensor, withall of the problems associated with such sensors, was required in theampule to signal when the ampule was full during the refilling process.This, in some cases, required another opening in the ampule which isundesirable, because this introduces additional potential for leaks andcontamination points.

In an attempt to overcome the problems associated with the opticalsensors, a metallic level sensor was employed to detect low levels ofhigh purity chemicals in the five-gallon bulk container. The metalliclevel sensor generally consisted of a toroidal shaped float made ofstainless steel held captive on a hollow shaft made of electropolishedstainless steel. The float contained a fixed magnet. A digital reedrelay was secured at a fixed position inside the shaft at an alarmtrigger point. As the float travelled past the reed relay, the fixedmagnet would change its state, thus causing a low level alarm conditionto be signaled. A replacement tank would then be substituted. Thedigital magnetic reed relay used in the metallic float level sensorprovided much more reliable detection of low source chemical levels inthe remote tank, because the magnetic reed switch is a low maintenancemechanical switch and provides positive on/off switching. As before, theempty 5-gallon container was never refilled by the user. It was alwaysreturned to the chemical supplier for cleaning and filling.

A low level metallic float sensor has also been used more recently inthe stainless steel ampule. Due to fears associated with contamination,however, the ampules were not refilled by the user and were only used instand alone systems. As with the five-gallon tank, when the metalliclevel sensor indicated the high purity TEOS or other high purity sourcechemical level was low, the ampule was simply replaced with a fullampule. In no instance was a metallic level sensor used to detect thelevel of high purity TEOS or other high purity source chemical in anampule when the ampule was used in any refill type system. Ampules usedin refill type systems have not used a float-type sensor or any othersensor with movable parts.

The use of metallic level sensors has been spurned in ampules used inrefill type systems because of the strong belief in the industry thatsliding metal to metal contact will cause the shedding of metalparticles and dissolution of metal ions, thus contaminating the highpurity TEOS or other high purity source chemical employed in thedelivery system. This belief exists despite the use of low level metalfloat sensors in stand alone stainless steel five-gallon tanks and instainless steel ampules. This is because in the stand alone systems, thetank or ampule is exchanged with a replacement tank or ampule,respectively, following each use. Furthermore, following each use, thetank or ampule is cleaned before refilling for a subsequent use. Boththe cleaning and refilling are accomplished at a remote location by thesupplier of the source chemical. Therefore, the amount a metal floattravels in a stand alone system is limited to one fill and drain cycle.On the other hand, in a refill system the ampule is periodicallyrefilled from a remote bulk container after each time it is emptied.Further, in a refill system, the ampule is never completely drained ofhigh purity TEOS or other high purity source chemical between eachrefilling. Thus, integrated circuit manufacturers and source chemicalsuppliers have had an unsubstantiated concern that with repeatedfillings of the same ampule over a period of time, the metal ionconcentration and metal particles in the ampule would increase to anunacceptable level. As a result of this concern, ampules that have beenused in refill type systems have always been equipped with the opticalsensors or with sensors with non-movable parts, such as, for example,capacitance probe sensors, despite the knowledge that metallic floatlevel sensors were much more reliable in refill systems.

Because, as noted above, optical sensors and capacitance probe sensorsrequire a high degree of maintenance and are subject to frequentfailure, the reliability of the bulk chemical refill systems usingsensors without moving parts have been in question. When these sensorsfail to detect a low or “empty” level, the ampule can run dry during theCVD process. As previously discussed, this can destroy the batch ofwafers then in process or force their rework at a cost of thousands totens of thousands of dollars. On the flip side, when sensors fail todetect the high or “full” level during a refill cycle, the ampule can beoverfilled potentially causing damage to costly equipment; wastingexpensive high purity source chemical such as TEOS and dopants (highpurity TEOS costs approximately 52,00/gal.); contaminating thefabrication area, which is typically a class 1 or class 10 clean roomenvironment; contaminating or damaging other equipment in the cleanroom; ruining the wafers being processed; and causing severe personalsafety concerns. In the past, to avoid these problems semiconductorequipment manufacturers have used refill systems with redundant levelsensors to minimize the impact of sensor malfunctions, used other levelsensor types (excluding the above-described float type sensors),employed timed refill, or employed measured refill of only a small fixedvolume or measured mass of chemical. These refill systems suffercharacteristic performance problems arising from: non-linearity ofalternate sensor technology, uncertainty of the refill volume, the lackof a positive shut-off of the chemical fill, the risk of malfunction dueto maladjustment of system components or the lack of level monitoring ofthe bulk chemical source. Therefore, a need exists for a reliable bulkchemical refill system for applications where high degree of chemicalpurity must be maintained, and a high level or error free refillconfidence must exist.

A number of problems have been found to exist with capacitive sensorscurrently used with rectangular ampules used for example in AppliedMaterials' P5000 CVD unit. These problems include leak integrity,repeatability and reliability problems. While the desire to obtain acontinuous level output from the rectangular ampule is a worthwhilegoal, the basic design of the capacitive sensor is poor, making systemsusing a capacitance probe somewhat unreliable and hence, unsafe.

Due to the complexity of capacitive level sensors, it is time consumingand difficult to properly disassemble, clean and assemble them. Becauseof this, certain chemical suppliers, rather than take on this task, mayleave the capacitance probes assembled during ampule refill cycles. Ifcritical parts are not properly cleaned and replaced upon each chemicalrefill, however, the probability of leaks occurring and improper levelsensing may increase. When Trimethylborate (TMB) or Trimethylphosphite(TMP) is the source chemical, failure to replace critical parts orimproper replacement of these parts typically leads to source chemicalleaks at the capacitive sensor and, occasionally, at the site glasslocated in the front of rectangular ampules. These leaks can posesignificant safety and process integrity problems.

Because the capacitive level sensor design has not exhibited thelongevity required to sustain several chemical fills between consumableparts replacement, the present capacitance probe design has not beenwidely used in refill systems. Rather, rectangular ampules filled withTMB or TMP and utilizing capacitive sensors have been removed andrefurbished.

The combination of the O-ring gland design, the chemical interaction andthe elevated temperatures have been known to cause mechanical failure ofthe sealing O-rings on the capacitance probes. Specifically, there aretwo out of four O-rings that have been known to fail on a regular basis.These two O-rings form a seal on the inner rod and on the outer surfaceof the outer sheath of the probe and are particularly prone to leaksbecause the sealing surfaces are angled providing poor control of Q-ringcompression. The most severe failures in one or both of these O-ringscan result in a very dangerous situation in which TMB or TMP can leak inlarge quantities during manufacture or, if in shipment, in the shippingcrate. The manufacturer of the O-rings, DuPont, has also expressedconcern over the gland design of certain capacitive sensor probes inthat it does not have adequate volume for the O-ring to expand with arise in temperature and with the minor interaction with the chemicalthat it is exposed to.

Further, the capacitance style sensor has been known to have problems inother industrial applications in terms of reliability and repeatability.The capacitive level sensor used in CVD systems is no exception. Whenrectangular ampules are shipped back to chemical suppliers forrefurbishing and refilling, routinely they are shipped back well abovethe level mark resulting in wasted chemical. Also, at other times, theampules are run dry, destroying the wafers in process. Moreover, in somesystems the capacitance reading for these sensors exceeds that of theinterface board designed to interpret its level and convert it to ananalog signal. The result is the capacitive sensor has poorrepeatability and accuracy in CVD systems.

Capacitive sensors also have poor sensitivity to level changes wherebecause of the electrical conductivity of the chemical the overallcapacitance changes very little even with large volume differences suchas for example with TMB and Triethylborate (TEB). Accordingly, areliable level sensor and refill system for rectangular ampules isdesirable.

SUMMARY OF THE INVENTION

The present inventions address and solve these problems. This isaccomplished through various combinations a bulk chemical deliverysystem and components for delivery of chemicals, including high puritychemicals. One of these inventive components is a highly reliable sensorwhich allows for the easy refilling and cleaning ampules, automatic andsemiautomatic manifold and methods for using the manifolds andcomponents in high purity bulk chemical delivery systems.

A refillable ampule according to one embodiment of the present inventioncomprises a digital level sensor for sensing a levels of chemicals inthe ampule. The digital level sensor transmits this signal to a controlunit that can be used to automatically start and stop the refillingprocess. Additionally the refillable ampule may include a digital sensorthat either provides an automatic signal for starting the refillingprocess or an audible or visual alarm to alert an operator that thecontainer is empty and requires refilling. The sensor can also send asignal to the processing equipment indicating the empty state of theampule. Preferably, due to the need for highly reliable level detection,the sensor is a digital level sensor comprising, for example a two-polemagnetic reed switch that can be interfaced through an interface circuitwith electronics on existing semiconductor processing equipment such aschemical vapor deposition equipment.

An aspect of a refill system made in accordance with the invention is acontrol unit. The preferred control unit includes circuitry forprocessing the high level signal from a digital sensor in a refillableampule to automatically discontinue the refilling process. Additionally,the control unit can include circuitry for processing the low levelsignal and automatically beginning the refilling process. The system canbe fully automatic, and, if so, the control unit will also includecircuitry for controlling the necessary valves associated with therefill lines as well as for processing a signal from a remote bulkcontainer.

In one embodiment of one the present inventions, the configuration ofthe control unit is such that it provides for manual start and automaticshut off of the refill cycle. In this configuration the control unit,when it receives the low level signal from the low level sensor in therefillable ampule, illuminates a visual alarm indicator or sounds anaudible alarm for signalling the operator to begin the refillingprocess. This warning indicator need not be incorporated into thecontrol unit, but may be also incorporated into a CVD reactor, anindependent alarm module, or a temperature controller entirely separatefrom the control unit. Once such a warning is signaled, it is up to theoperator to close off the values that apply pressurized inert gas to therefillable ampule and to vent the refillable ampule to atmosphere. Thepressurized inert gas is a traditional medium for supplying the highpurity chemical to the semiconductor equipment. It is then up to theoperator to initiate the actual flow of the high purity chemical fromthe remote container to the refillable ampule by, for example, pressinga fill button on the control unit. In this configuration, once the fillsequence is initiated, a valve, which is preferably a pneumatic valve,in the refill line is caused to open. The refillable ampule is thenrefilled with a high purity source chemical such as TEOS, TMB, TMP orother high purity chemical from the bulk container. The actual transferof the high purity source chemical from the remote bulk container to therefillable ampule, may be accomplished by pressurizing the remote bulkcontainer with an inert gas that pushes out the high purity sourcechemical. In this configuration, at this point the operators involvementis complete.

In this configuration when the refillable ampule is full a high leveldigital sensor can be used to transmit a signal to the control unit. Thesignal is processed and the pneumatic valve is closed. Additionally, oralternatively, an audible and visible alarms may be sounded andilluminated. As a safety precaution the digital sensor in the refillableampule may also include a “high-high” level sensor. This sensor can beused as an emergency shutoff when the normal high level sensor fails.Preferably, this sensor signals the control unit that the refillableampule is full by an independent circuit from the normal high level orfull signal within the control unit.

A manual shut off configuration is also possible and within the scopethe disclosed inventions. In such a configuration, the control unit canstill be used to indicate that the refillable ampule is full but wouldnot necessarily automatically close the pneumatic valve. In thisconfiguration, to stop the flow of high purity chemical from the remotebulk container to the refillable ampule, the operator may be required tomanually depress a button on the control unit to close the valve andterminate the fill cycle.

The control unit may also be configured to interface with a digitallevel sensor in the bulk container. A digital level sensor in the bulkcontainer may include any number of actual discrete sensors forproviding an indication of the remaining volume of high purity chemicalat any point in time. If a dual level digital metallic level sensor isused, the trigger points are preferably set at 20% source chemicalremaining and at 5% or less source chemical remaining. Depending uponthe application other trigger points can be used.

Through the unique arrangement of piping and valves interconnecting thebulk containers and refillable ampules, and their method and sequence ofoperation, bulk containers can be replaced without fear ofcontamination. This latter aspect of the inventions is especially usefulin refillable high purity chemical bulk delivery systems.

The above and other objects, features and advantages of the inventionswill become apparent from the following detailed description of thepreferred embodiments, considered in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a high purity chemical refilldelivery system according to one embodiment of the present invention;

FIG. 2 is a front view of a control unit control panel according to oneembodiment of the present invention;

FIG. 3 is a side view in partial cross section of a five-gallon highpurity bulk chemical container;

FIG. 4 is a schematic representation of a single level float controlsensor in the “open” position;

FIG. 5 is a schematic representation of a single level float levelsensor in the “closed” position;

FIG. 6 is a side view in partial cross-section of a refillable ampuleaccording to one embodiment of the present invention;

FIG. 7 is a top view of the refillable ampule illustrated in FIG. 6;

FIG. 8 is a schematic side view in partial cross-section of a refillableampule according to an embodiment of the present invention;

FIG. 9 is a side view of a metallic level switch assembly for arefillable container according to an embodiment of the presentinvention;

FIG. 10 is a side view of metallic level switch assembly for arefillable container according to an embodiment of the presentinvention;

FIG. 11 is a side view of metallic level digital switch assembly for abulk container according to one embodiment of the present invention;

FIG. 12 is a side view of a metallic level digital switch assembly for abulk container according to an embodiment of the present invention;

FIG. 13 is a schematic diagram of typical prior art conditioningcircuitry for interfacing an optical level sensor with existingsemiconductor processing equipment;

FIG. 14 is an electrical schematic diagram of a prior art optical levelsensor;

FIG. 15 is a schematic diagram of control circuitry for an embodiment ofa control unit;

FIG. 16 is a front view of a manifold layout according to one embodimentof the present invention; and

FIG. 17 is a front view of a manifold layout for an embodiment of thepresent invention;

FIG. 18 is a schematic diagram of a manifold layout for an embodiment ofthe present invention;

FIG. 19 is a partial cross section of a purge style rectangular dopantampule and associated piping incorporating a prior art capacitance probesensor.

FIG. 20 is a partial cross section of a purge style rectangular dopantampule and associated piping incorporating a digital probe sensor.

FIG. 20a is a partial cross section of a rectangular TEOS ampule andassociated piping incorporating a digital probe sensor.

FIG. 21 is a drawing of the front panel of a preferred low levelmonitor.

FIG. 22 is a circuit diagram for a low level monitor.

FIG. 23 is a circuit diagram of a preferred interface circuit between alow level monitor and the electronics of a CVD unit.

FIG. 24 is a diagram of a five level single float digital sensor for arectangular ampule.

FIG. 25 is a circuit diagram of interface circuitry for a five level,single float digital sensor and a P5000-type CVD reactor.

FIG. 26 is a diagram of a dual float five level digital sensor for arectangular ampule.

FIG. 27 is a diagram of a five float five level digital sensor for arectangular ampule.

FIG. 28 is a circuit diagram for a five float five level digital sensorand interface circuitry for a rectangular ampule.

FIG. 29 is a diagram of a two float five level digital sensor for arectangular ampule incorporating an integral refill line and isolationvalve.

FIG. 30 is a representation of a high purity dopant chemical refillsystem according to one embodiment of the present invention.

FIG. 31 is a front view of a control unit control panel according to apreferred embodiment of the present invention.

FIG. 32 is a schematic diagram of control circuitry for a presentlypreferred embodiment of the present invention.

FIG. 33 is a front view of a automatic purge controller control panelaccording to one embodiment of the present invention.

FIG. 34 is a schematic representation of a high purity chemical deliverysystem according to an embodiment of the present invention.

FIG. 35 is a schematic representation of a multi-point auto-refillsystem according to one embodiment of the present invention.

FIG. 36 is a schematic representation of one embodiment of a bulk cubeincluding a purge manifold and a distribution manifold for use in amulti-point auto-refill system according to the present invention.

FIG. 37 is a diagrammatic representation of a presently preferredrefillable high purity chemical delivery system according to oneembodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

A preferred embodiment of a high purity chemical refill system isdescribed in connection with FIG. 1. The system consists of three mainfunctional components: a bulk canister 20 located in a remote chemicalcabinet with a delivery manifold/purge panel 22; a refillable stainlesssteel ampule 30 to supply semiconductor fabrication equipment such as aCVD reactor with high purity TEOS or other high purity source chemicals;and a control unit 40 to supervise and control the refill operation andto monitor the level of the bulk container.

Bulk chemical refill system 18 has two basic modes of operation: anormal process operation and a refill mode of operation. Under normalprocess operation, refillable ampule 30 delivers high purity TEOS orother high purity source chemicals to semiconductor fabricationequipment fabrication equipment via delivery line 32. Delivery line 32is connected to the semiconductor processing equipment usingconventional process connections.

In this embodiment the refillable ampule 30 incorporates an opticalsensor 34 for communicating a low level signal to the CVD reactorthrough the conventional low level sensor/reactor interface circuitshown in FIG. 13. When a low level signal is communicated to thefabrication equipment, the fabrication equipment will employ the signalin accordance with its normal conventional operation, such as its normallow level default procedure.

FIG. 2 illustrates an embodiment of control panel 52 of control unit 40.Control panel 52 contains five switches: a “MAIN POWER” on off switch, a“PUSH TO TEST INDICATORS” switch, an “ABORT FILL” switch, a “PUSH TOFILL” switch, and a “PUSH SONIC OFF” switch. The operation of theseswitches is described in detail in conjunction with FIG. 15 below.

Control panel 52 also includes a number of illuminated indicators toreport the status of chemical levels in bulk container 20 and ampule 30.The illuminated indicators include “BULK OK”, “BULK LOW”, “BULK EMPTY”,“AMPULE REFILLING”, “AMPULE NOT REFILLING”, “AMPULE HIGH-HIGH LEVEL”,and “AMPULE HIGH LEVEL”.

A preferred method of operation of control unit 40 during normal processoperation is described in connection with FIG. 2. During normal processoperation, the level of source chemical in bulk container 20 should notchange. Therefore, the “BULK ON” indicator should remain lit. However,if the “BULK LOW” or “BULK EMPTY” indicator came on during the lastrefill cycle, these indicators will remain illuminated until the bulkcontainer 20 is replaced with a full container. The operation of thelevel sensors in bulk container 20 is explained in more detail below.

Throughout normal process operation, the “AMPULE NOT FILLING” indicatorshould remain on to indicate that the refill system is not in the refillmode. Because the level of high purify TEOS or other high purity sourcechemical in refillable ampule 30 changes throughout normal processoperation, the “AMPULE HIGH” level indicator, which is illuminated uponcompletion of a refill cycle, will remain illuminated until the highpurity TEOS or other high purity source chemical level in refillableampule 30 falls below the “AMPULE HIGH” trigger point 41 of metalliclevel sensor 39.

It should be noted that if the “AMPULE HIGH-HIGH” indicator wasilluminated during the refill process, as with the “AMPULE HIGH”indicator, the “AMPULE HIGH-HIGH” indicator will remain on until thehigh purity source chemical in ampule 30 fails below the “HIGH-HIGH”trigger point 41 a of metallic level sensor 39. In such a case, thechemical level will fall through the “AMPULE HIGH” trigger region thuscausing the “AMPULE HIGH” indicator to illuminate and then extinguish asdescribed above.

The refill procedure is started either automatically orsemiautomatically. The semiautomatic procedure begins by the operatormanually configuring ampule 30 to the refill configuration. This is doneby closing the outlet valve 36 on the ampule 30. In addition, theoperator would verify that the inlet valve 38 is closed.

Because the high purity TEOS or other high purity source chemical issupplied under pressure to some CVD reactors by an inert gas such as Heduring normal operation, the ampule 30 may need to be depressurized anda vacuum pulled to ease the high purity TEOS or other high purity sourcechemical transfer process. The depressurization and degassing processare accomplished using standard techniques utilized in the chemicalvapor deposition art through passage 31. After the depressurizationstep, the vacuum/pressurization valve 37 is closed. Inlet valve 33 isnow opened to allow the flow of high purity TEOS or other high puritysource chemical into ampule 30. The depressurization would unnecessaryfor other applications where pressurization of the headspace of ampule30 would not present a problem.

The semiautomatic refilling process requires an operator to depress the“PUSH TO FILL” switch on control panel 52 of control unit 40 shown inFIG. 2. Once the “PUSH TO FILL” switch is pushed, the control unit 40opens a valve 42 in the refill line 44. High purity TEOS or other highpurity source chemical, depending on the application, then flows intothe ampule 30 from the bulk container 20.

Valve 42 is preferably a pneumatically activated valve. When apneumatically activated valve is used for valve 42, it is opened when acontrol pressure is supplied through passage 48 from control unit 40.The control pressure used to open valve 42 can be nitrogen or otherpressurization gas such as plant compressed dry air. The flow of acontrol pressure through passage 48 is controlled by solenoid vales incontrol unit 40. The operation of these solenoid valves is described indetail below in conjunction with FIG. 15.

Bulk container 20 is continuously pressurized with an inert gas such ashelium; thus, when valve 42 is opened, inert gas forces the high puritysource chemical from bulk container 20 through refill line 44 and to theampule 30.

Metallic level sensor assembly 21 in ampule 30 contains a high levelmetallic level sensor 39. Metallic level sensor 39 is preferably a duallevel sensor capable of detecting two separate levels of source chemicalin ampule 30. However, metallic level sensor 39 can also be a singlelevel sensor, or a multiple trigger point level sensor up to acontinuous level sensor. In the preferred embodiment metallic levelsensor 39 is a dual level sensor with two trigger points, 41 and 41 a.Trigger point 41 is for detecting a “HIGH LEVEL” (full) condition inampule 30, and trigger point 41 a detects a “HIGH-HIGH LEVEL” conditionin ampule 30.

When the metallic level sensor 39 detects that the ampule 30 is full, itsupplies a signal to the control unit 40 via cable 47. In response tothat signal control unit 40 closes pneumatic valve 42 without operatorintervention. Simultaneously, control unit 40 signals an audible andvisual alarm on control panel 52. If the “HIGH LEVEL” trigger point 41of metallic level sensor 39 should fail, the “HIGH-HIGH LEVEL” triggerpoint 41 a of metallic level sensor 39 is in place and will trigger andinstruct control unit 40 that the ampule 30 is full via cable 47 by anindependent circuit within the control unit 40. This “HIGH-HIGH” alarmis a fail safe feature that prevents overfilling the ampule 30 and stopsrefilling in case of electrical failure of the “HIGH LEVEL” alarmcircuit and is described below in connection with FIG. 15. Obviously, ifmetallic level sensor 39 is only a single level sensor, only a “HIGHLEVEL” condition can be detected, and no fail safe level detection isprovided.

Control unit 40 also interfaces with a metallic level sensor assembly 21in bulk container 20 via cable 26. The metallic level sensor 39 in theremote bulk container has its trigger points preferably set at 20%remaining source chemical and at 5% remaining source chemical. Dependingon specific process requirements, however, other trigger points can beused. If the source chemical level falls below the first trigger point,which typically only occurs during the refilling sequence, a visualindication of “BULK LOW” on the control panel 52 of control unit 40 isproduced. If the source chemical level falls below the second triggerpoint, a “BULK EMPTY” visual alarm on control panel 52 in addition to anaudible alarm is produced in conjunction with an automatic terminationof the refill sequence.

Control unit 40 can also be configured for manual shut off during therefill cycle. In such a configuration, the operator would terminate therefill cycle by manually depressing a button on control panel 52 uponacknowledging a visual or audible indication that the refillable ampule30 is full. Similarly, a fully automatic start/automatic shut offconfiguration can be provided. This can be accomplished by replacingmanual vacuum/pressurization valve 37 with an automatic valve preferablypneumatic, and placing a pressure sensor in the passage 31 to ampule 30.The pneumatic valve and pressure sensor are then connected to controlunit 40. When a specified vacuum is pulled on ampule 30 at the beginningof the refill cycle to ease the flow of high purity source chemical intoampule 30, the pressure sensor in passage 31 would signal control unit40. In response, control unit 40 would close the pneumatic valve 37 andsimultaneously open pneumatic valve 42 in the refill line 44, thusautomatically initiating the refill process.

An alternative refill procedure for ampule 30 will now be described.This refill procedure is applicable if the CVD processing equipment towhich ampule 30 is attached has a separate valve, from that of valve 36on ampule 30, in delivery line 32 for closing off the supply of TEOS orother high purity source chemical to the CVD reaction chamber inaddition to separate valves from that of valve 37 for closing of theinert gas supply and the vacuum supply through passage 31 to ampule 30.One CVD machine that has such a layout is a Novellus Sigma Six machine.The following procedure is preferred for effecting a refill of ampule 30with TEOS from bulk container 20 in such a system:

1. Ensure the System is Idle.

2. Ensure that the outlet valve 36, the vacuum/pressurization valve 37,and inlet valve 38 on ampule 30 are open.

3. Close the separate source chemical shutoff valve in delivery line 32.

4. Close the separate “Inert Gas Supply” valve in passage 31 of the CVDunit.

5. Open the separate “Vacuum” supply valve in passage 31 of the CVD unitand wait approximately 5 minutes until the pressure in ampule 30 is lessthan approximately 100 mTorr.

6. Close the separate “Vacuum” supply valve in passage 31.

7. Press the “PUSH TO FILL” button on control unit 40.

8. As with the above described refill procedure, two normal conditionswill terminate the refill sequence:

1) “AMPULE HIGH LEVEL”. Ampule 30 is full. The “AMPULE HIGH LEVEL”indicator on control panel 52 will light, the sonic alarm will sound andcontrol unit 40, will automatically close valve 42 in refill line 44. Ifthe controller alarms for “AMPULE HIGH LEVEL”, proceed to step 9.

2) “BULK EMPTY”. Bulk container 20 has an insufficient amount of sourcechemical in it to completely fill ampule 30. The “BULK EMPTY” indicatoron control panel 52 will be on, the sonic alarm will sound and controlunit 40 will automatically close valve 42 in refill line 44. If controlunit 40 alarms for “BULK EMPTY”, proceed to step 14.

Ampule 30 should typically be filled in less than 10 minutes if it has acapacity of 2 gallons or less. Therefore, if the SONIC ALARM does notactivate within 10 minutes after starting the refill, steps 8 a through8 j should be followed to ensure that a proper vacuum has been pulled onampule 30.

8 a. Press the “ABORT FILL” switch on control panel 52.

8 b. Press the “SONIC OFF” switch on control panel 52.

8 c. Ensure that valves 36, 37, and 38 on ampule 30 are open.

8 d. Open the separate “Vacuum” supply valve in passage 31 of the CVDunit and wait approximately 5 minutes until the pressure in ampule 30 isless than 100 mTorr.

8 e. Close the separate “Vacuum” supply valve in passage 31.

8 f. Press the “PUSH TO FILL” switch on control panel 52.

8 g. Wait for an audible alarm. When the audible alarm activates,observe the visual indicators on the front panel of the Controller. Ifthe “AMPULE HIGH LEVEL” indicator is on, go to step 9. If the “BULKEMPTY” indicator is on, go to step 14.

9. Press “SONIC OFF” button on control panel 52.

10. Open the separate “Inert Gas Supply” valve in passage 31 of the CVDunit and wait 30 seconds.

11. Open the separate source chemical shutoff valve in delivery line 32.

12. Check all valve switches in the chemical supply cabinet of the CVDmachine to verify that all of them are in their normal operatingpositions.

13. Return the CVD reactor to normal operation. If the audible alarm and“BULK EMPTY” indicators are both activated, then steps 14-19 should befollowed:

14. Press “SONIC OFF” button on control panel 52.

15. Open the separate “Inert Gas Supply” valve in passage 31 of the CVDunit and wait 30 seconds.

16. Open the separate source chemical shutoff valve in delivery line 32.

17. Check all valve switches in the chemical supply cabinet of the CVDmachine to verify that all of them are in their normal operatingposition.

18. Return the CVD reactor to normal operation.

19. Exchange the empty bulk container 20 for a full one at the earliestopportunity.

The “BULK LOW” visual indicator may be illuminated when the refillsequence is complete. This is a normal condition. Replacing bulkcontainer 20 with a full container when the “BULK LOW” visual indicatoris illuminated is not recommended because expensive high purity sourcechemical remains in bulk container 20 at this point. Bulk container 20,therefore, should not be replaced until the “BULK EMPTY” indicator isilluminated.

Ampule 30 may be refilled at any convenient time. It is not necessary towait until a low alarm on the CVD processing equipment sounds beforerefilling.

The fill rate of ampule 30 is preferably approximately 2 liters/minute.Therefore, if a “BULK EMPTY” alarm activates within one minute ofstarting the refill sequence, bulk container 20 should be replacedimmediately and the refill sequence repeated before resuming operationof the CVD reactor when ampule 30 has a capacity of 2 gallons or more.

A particularly preferred bulk container 20 will now be described inconnection with FIG. 3. Bulk container 20 is made of 316 Lelectropolished stainless steel to minimize the risk of contamination tothe high purity source chemical contained within the tank. Bulkcontainer 20 typically comes in a five-gallon capacity. However, largercapacity canisters can be used for bulk container 20, including ten andtwenty-gallon containers. Smaller containers may be used too, forexample, one and two-gallon containers. Bulk containers 20 is used tosupply a bulk high purity source chemical such as high purity TEOS froma remote location to ampule 30. The source chemical is delivered bycontinuous pressurization of the canister with inert gas such as heliumfor on demand refill of the refillable ampule 30. The inert gas issupplied through the inlet valve 64. Inlet valve 64 is connected to andcommunicates with passage 88 of the delivery/purge manifold 22 which isin communication with an inert gas source. The outlet valve 66 alsoconnects to the refill line 44 by way of manifold 22. Thus whencontainer 20 is pressurized with helium gas or another suitable gas andpneumatic valve 42 is opened, high purity TEOS or other high puritysource chemical is forced through outlet pipe 60, outlet valve 66,manifold 22, refill line 44, inlet valve 38 and into refillable ampule30.

In one embodiment, bulk container 20 is provided with a metallic levelsensor assembly 21 including a metallic level sensor 39 preferablycomprises of a two pole read switch triggered by a metallic float 24. Itis understood that other types of triggers, such as a Hall effect sensormay be employed. The two-pole reed switch interfaces directly withcontrol unit 40 through cable 26. Metallic level sensor 39 preferably isa dual level sensor, in that it incorporates two reed switches. As withthe metallic level sensor 39 in refillable ampule 30, however, it canincorporate any desirable number of reed switches to detect one or morelevels of source chemical. Further any number of separate metallic levelsensors 39, each employing their own metallic float 24 may be employed.

The principle of operation behind metallic level sensor 39 is describedin connection with the single level metallic level sensor 39 illustratedin FIGS. 4 and 5. Metallic level sensor 39 is comprised of a toroidalshaped metallic float 24 made of stainless steel or other non-magnetic,chemically inert material. Alternatively, metallic float 24 is coatedwith a fluoropolymer or other chemically inert coating. The preferredconstruction material is 316 L stainless steel. Metallic float 24contains a fixed magnet 23 and is held captive on a hollow metallicshaft 28. Shaft 28, however, is sealed on its bottom extending intoampule 30 to prevent high purity source chemical from flowing up intothe shaft. Further, metallic shaft 28 is preferably made ofelectropolished 316 L stainless steel or other chemically inertmaterial. Alternatively, shaft 28 is made of a non-magnetic materialcoated with a fluoropolymer or other chemically inert material. Insideshaft 28, a digital magnetic reed relay switch RS is secured in a fixedposition at a predetermined alarm trigger point. This trigger pointcorresponds, for example, to the “BULK EMPTY” trigger set point. Aferrule 46 is permanently attached to one end of shaft 28 for attachmentto the container.

Additional reed relay switches RS may be added within shaft 28 to form amultiple level detector. For example, if a second reed relay switch RSis added at second fixed trigger point within shaft 28 a dual levelfloat sensor is created. Additional reed relay switches RS may be addedfor any number of additional levels of detection.

Retainer rings 27 are used to restrain the movement of the metallicfloat 24 so that upon filling of bulk container 20, the float isrestrained from sliding up the entire length of shaft 28, and slidingback down the entire length of shaft 28 as bulk container 20 is drained.It should be noted that, if desired the upper retainer ring 27 may beeliminated in this configuration. Only the lower retainer ring 27 isnecessary to prevent metallic float 24 from sliding off shaft 28.Retainer rings 27 are also preferably constructed from 316 stainlesssteel, Kalrez™ or other suitable, chemically inert material.

Metallic level sensor assembly 21 comprising shaft 28, metallic float 24and retainer ring 27 is preferably electropolished following assembly.In addition, the surface finish of all wetted metal parts is preferablyRa 20 or better prior to electropolishing.

Metallic level sensor 39 works as follows, when the liquid sourcechemical is above the upper retainer ring, the metallic float 24 remainsat the top ring 27 in the “float up” position. As the liquid leveldrops, metallic float 24 moves down the shaft 28. When the magneticfield from fixed magnet 23 latches the magnetic reed switch RS, metallicfloat 24 is in the “float down” position. When the magnetic reed switchis closed, the indicator circuit is completed. This output signal istransmitted through one of two wires 25 in cable 26 to an alarm circuitin control unit 40.

FIGS. 4 and 5 illustrate the use of a normally open magnetic reed switchRS. Alternatively, however, a normally closed magnetic reed switch canbe used. In such a case, as the metallic float 24 travels pass the reedrelay, the fixed magnet 23 will open the reed relay switch RS. Thus, thealarm condition is signaled either by opening the closed relay contactsor by closing the open reed relay contacts.

As discussed above, in the preferred embodiments, a dual level metallicsensor 39 is utilized. A dual level metallic sensor 39 is providedsimply be securing a second digital magnetic reed relay switch RS at adesired alarm trigger point. The single metallic float 24 on shaft 28can trigger both reed switches. If a dual level metallic sensor is used,four wires are found in cable 26 and are used to communicate the stateof the switches to the control unit 40. Preferably, the second triggerpoint should be set for 20% source chemical remaining. In the preferredembodiment, this corresponds to the “BULK LOW” trigger point.

A second sensor configuration could incorporate a fixed magnet 23 insidea float made of the same materials as metallic float 24 and attached toshaft 28 by means of a hinge. As the float swivels, it brings the fixedmagnet into proximity of a reed relay switch RS and changes the state ofthe reed relay from open to closed or closed to open.

Refillable ampule 30 can now be described in connection with FIGS. 6 and7. Refillable ampule 30 is preferably made for 316 L electropolishedstainless steel construction. Typically, ampule 30 has a 2.3 litercapacity, but can be provided in a wide range of sizes, including 1.3liter, 1 gallon, 1.6 gallon, 2 gallons, and 5 gallons. The size of theampule merely depends on process demands.

Vacuum/pressurization valve 37 permits refillable ampule 30 to bepressurized with an inert gas such as helium during normal processoperation, which is typical of many CVD ampules. This valve also has thefunction of permitting the depressurization and application of a vacuumto ampule 30 prior to a refill sequence or removal of ampule 30 from thesystem 18.

Outlet valve 36 connects refillable ampule 30 to a delivery line 32 thatsupplies liquid high purity TEOS or other high purity source chemicaldirectly to the semiconductor processing equipment during normal processoperation. Thus, during normal process operation, helium or other inertpressurizing gas is supplied through vacuum/pressurization valve 37 topressurize ampule 30. The pressure applied to the internal cavity ofampule 30 forces high purity TEOS or other high purity source chemicalthrough hollow pipe 33 and outlet valve 36 to delivery line 32 thatfeeds a CVD reaction chamber. It should be noted that the entirety ofpipe 33 is not shown on the drawing to allow the optical sensor assembly45 to be seen. Normally the pipe 33 extends below the end of the opticalsensor 34 to allow for proper operation of the system.

In the depicted embodiment, low level sensor 34 is an optical sensor. Itis of the type commonly used with standard CVD processing equipment, andneed not be explained in detail. An electrical schematic diagram of theoptical sensor 34 is illustrated in FIG. 14. Low level optical sensor 34sends signals through cable 35 to an independent alarm module, thedisplay panel for the reactor itself, or through a temperaturecontroller, but not through control panel 40. Because low level sensor34 is an optical sensor in the present embodiment of the invention, itcan interface with the semiconductor processing equipment, independentalarm module or temperature controller using the existing circuitryillustrated in FIG. 13 for interfacing a low level optical sensor with areactor, independent alarm module, or temperature controller.

Inlet valve 38 is a manual shut-off valve for the refill line 44. Valve38 remains closed during normal process operation and is opened onlyduring a refill sequence. In the fully automatic process this is anautomatic valve, preferably pneumatically activated.

Metallic level sensor assembly 21 contains at least a single levelmetallic sensor level 39. Preferably, however, metallic level sensor 39is a dual level sensor for detecting “HIGH LEVEL” and “HIGH-HIGH LEVEL”respectfully. The metallic level sensor 39 of the metallic level sensorassembly 21 operates in the same manner as described in connection withFIGS. 4 and 5. Metallic level sensor 39 illustrated in FIG. 6 is a duallevel sensor with trigger points at “HIGH LEVEL” 41 and “HIGH-HIGHLEVEL” 41 a.

A particularly preferred refillable ampule 30 is illustrated in FIG. 8.The ampule 30 in FIG. 8 has two metallic sensor assemblies 21, eachcomprising a metallic level sensor 39. The first 55 is for detectinghigh level conditions. As before, preferably metallic level sensor 39 isa dual level sensor as described in FIG. 6. The second 58 detects a lowlevel condition. Low level metallic level sensor 58 is a single levelfloat sensor that signals the CVD reactor, an independent alarm module,or a temperature control unit that the source chemical level with inampule 30 has reached a low level, terminating normal processoperations. Cable 35 carries two wires. These two wires are used tointerface with the semiconductor processing equipment. In particular,the two wires are connected across pins 1 and 2 of the interfacecircuitry depicted in FIG. 13. When the metallic level sensor 39 isemployed, pine 3 is left floating.

As is apparent from the above discussion, metallic level sensor assembly21 can have a number of configurations. FIGS. 9-12 illustrate just a fewof the available preferred configurations.

FIG. 9 illustrates a metallic level sensor assembly 21 for refillableampule 30 comprising a metallic level sensor 39 with two trigger pointsa “HIGH LEVEL” trigger point 41 and a “HIGH-HIGH” level trigger point 41a.

FIG. 10 illustrates a metallic level sensor assembly 21 for refillableampule 30 comprising two metallic level sensors 39. The first 49 is adual level sensor as described in FIG. 9. The second 50 detects a lowlevel condition. Low level metallic level sensor 50 is a single levelfloat sensor that signals the CVD reactor, an independent alarm module,or a temperature control unit that the source chemical level withinampule 30 has reached a low level, terminating normal processoperations. High level metallic level sensor 49 is a dual level floatsensor with two trigger points a “HIGH LEVEL” trigger point 41 and a“HIGH-HIGH” level trigger point 41 a as previously described. Thisconfiguration has an advantage in that only one hole must be provided inthe lid 43 of ampule 30 for the source chemical level sensors, thusreducing the potential for contamination of source chemical. The cable35 carries six wires. Four of these wires terminate in the control panelas indicated in FIG. 15 and two are used to interface with thesemiconductor processing equipment. In particular, the two wires areconnected across pins 1 and 2 of the interface circuitry depicted inFIG. 13. When the metallic level sensor 39 is employed, pin 3 is leftfloating.

FIG. 11 illustrates a metallic level sensor assembly 21 for a bulkcontainer 20 comprising a dual level metallic level sensor 39 withtrigger points set at a “BULK EMPTY” trigger point and at a bulk fulltrigger point. The bulk full trigger point is used by the supplier ofthe high purity source chemical to fill bulk container 20 after cleaningand servicing the tank.

FIG. 12 illustrates a metallic level sensor assembly 21 for a bulkcontainer 20 comprising a triple level metallic level sensor 39 withtrigger points set to detect the following level conditions: “BULKEMPTY”, “BULK LOW”, and “BULK FULL”. Again, the bulk full trigger pointis used by the supplier to the high purity source chemical to fill bulkcontainer 20 after cleaning and servicing the tank.

The manner is which metallic sensor assembly 21 is attached to ampule 30is described in connection with FIGS. 8-12. A ferrule 46 is permanentlyattached to one end of shaft 28 for attachment of the metallic sensorassembly 21 to ampule 30. Ferrule 46 is preferably constructed from 316L stainless steel, and the preferred method of attachment is welding.

Metallic sensor assembly 21 is attached to ampule 30 using ferrule 46 inconjunction with clamp 61. Clamp 61 is preferably a flange clamp of thetype used for sanitary piping. Clamp 61 is used to clamp flange surface62 of ferrule 46 against a mating flange surface on a pipe 63 extendingout of the top of ampule lid 43. Clamp 61 is tightened around ferrule 46and the mating flange on pipe 63 by tightening knob 65. A teflon O-ring67, which is interposed between the mating flange surfaces, iscompressed as clamp 61 is tightened, thereby providing a leak tightseal.

Alternatively, metallic sensor assembly 21 can be attached to ampule 30by welding a threaded connector plug to shaft 28. The threaded connectorplug would then be threaded into a mating female connector on lid 43 ofampule 30.

The operation of control unit 40 will now be described in connectionwith FIGS. 1, 2 and 15.

Connection to the 110 V.A.C. 60 Hz. Plant Power is made via a standardU-ground male plug of the AC Cord Set CS1. Cord set CS1 plugs into thefiler assembly L1. Filter L1 provides line conditioning for bothincoming and outgoing transients and connects the AC power to the mainpower switch SW1. Filter L1 also provides the chassis ground connection.

Main power switch SW1, is a Double Pole Double Throw (DPDT) toggleswitch located on the upper left-hand corner of the control panel 52 ofthe control unit 40. Both the hot and neutral sides of the AC line areswitched ON and OFF. Switched AC power is connected to the Fuse F1through main power switch SW1. Fuse F1 is ¾ AMP, 3 AG size (¼″×1-¼″),standard fuse mounted inside control unit 40.

Conditioned, switched, and fused AC power is connected to the AC inputof the linear power supply PS1. Power supply PS1 is located inside thecontrol unit 40 and provides regulated 24 V.D.C. power for the controlunit 40 circuitry.

The “BULK LOW” circuit 83 will be described first.

When the level of source chemical in bulk container 20 is above the “LOWLEVEL” trigger point, float 24 is floated up and the “BULK LOW” sensorreed switch RS1, is open and the “BULK LOW” indicator LED1 is off. (Itshould be noted that the reed switches are only shown in representativeform as being inside the control panel. In reality the reed switches arein respective containers in the metallic level sensor assemblies 21.)

When the level of product in bulk container 20 goes below the “LOWLEVEL” trigger point, float 24 floats down and the “BULK LOW” sensorreed switch RS1, is closed and the “BULK LOW” indicator LED1 is turnedon.

With respect to the “BULK EMPTY” circuit 85, when the level of productin bulk container 20 is above the “EMPTY LEVEL” trigger point, float 24is floated up and the “BULK EMPTY” sensor reed switch RS2 is open, andthe control relay RY1 coil (pins 2 to 7) is deenergized. When RELAY RY1is deenergized, the normally open contacts (N.O.) (pins 8 to 6), areopen, and the “BULK EMPTY” indicator LED2 is off. When relay RY1 isdeenergized, the normally closed (N.C.) contacts (pins 8 to 5) areclosed and the “BULK OK” indicator LED3 is on. When relay RY1 isdeenergized, the N.C. contacts (pins 1 to 4) are closed and the refillcircuit is made.

When the level of product in the Bulk Container goes below the “EMPTYLEVEL” trigger point, the float 24 floats down and the “BULK EMPTY”sensor reed switch RS2 is closed, and the control relay RY1 coil (pins 2to 7) is energized. When relay RY1 is energized, the N.O. contacts (pins8 to 6) close and the “BULK EMPTY” indicator LED2 is turned on. Whenrelay RY1 is energized, the N.C. contacts (pins 8 to 5) open and the“BULK OK” indicator LED3 is turned off. When relay RY1 is energized, theN.C. contacts (pins 1 to 4) open and the refill circuit is broken.

The ampule “HIGH-HIGH LEVEL” circuit 86 is now described.

When the level of product in the ampule 30 is below the “HIGH-HIGHLEVEL”, the float 24 of dual level metallic level sensor 39 is floateddown with respect to the “HIGH-HIGH LEVEL” trigger point 41 a, and theampule 30 “HIGH-HIGH” sensor reed switch RS3 is open. Thus, the controlrelay RY2 coil (pins 2 to 7) is deenergized. When relay RY2 isdeenergized, the N.O. contacts (pins 8 to 6) are open and the “AMPULEHIGH-HIGH” indicator LED4 is off. When relay RY2 is deenergized, theN.O. contacts (pins 8 to 6) are open and the N.O. coil of air controlvalve V1 is deenergized and valve V1 is open. When relay RY2 isdeenergized, the N.C. contacts (pins 1 to 4) are closed and the refillcircuit is made.

When the level of product in ampule 30 goes above the “HIGH-HIGH LEVEL”trigger point 41 a, the float 24 of dual level metallic level sensor 39floats up with respect to the “HIGH-HIGH LEVEL” trigger point 41 a, andthe ampule 30 “HIGH-HIGH”sensor reed switch RS3 is closed. Thus, controlrelay RY2 Coil (pins 2 to 7) is energized. When relay RY2 is energized,the N.O. contacts (pins 8 to 6) close and the “AMPULE HIGH-HIGH”indicator LED4 is turned on. When relay RY2 is energized, the N.O.contacts (pins 8 to 6) close and the N.O. coil of control solenoid valveV1 is energized and valve V1 closes, stopping the refill cycle. Whenrelay RY2 is energized, the N.C. contacts (pins 1 to 4) open and therefill circuit is broken.

With respect to the “AMPULE HIGH” circuit 87, when the level of productin ampule 30 is below the “HIGH LEVEL” trigger point 41, the float ofdual level float sensor 39 is floated down with respect to the “HIGHLEVEL” trigger point 41, and the “AMPULE HIGH” sensor reed switch RS4 isopen. Thus, the control relay RY3 coil (pins 2 to 7) is deenergized.When relay RY3 is deenergized, the N.O. contacts (pins 8 to 6) are openand the “AMPULE HIGH” indicator LED5 is off. When relay RY3 isdeenergized, the N.C. contacts (pins 1 to 4) are closed and the refillcircuit is made.

When the level of source chemical in the ampule 30 goes to or above the“HIGH LEVEL” trigger point 41, the float 24 of dual level metallic levelsensor 39 floats up and the “AMPULE HIGH” sensor reed switch RS4, isclosed and the control relay RY3 coil (pins 2 to 7) is energized. Whenrelay RY3 is energized, the N.O. contacts (pins 8 to 6) close and the“AMPULE HIGH” indicator LED5 is turned on. When relay RY3 is energized,the N.C. contacts (pins 1 to 4) open and the refill circuit is broken.

Refill circuit 82 is now described, Before the refill cycle begins, the“PUSH TO FILL” switch SW2 is open, the “ABORT FILL” switch SW3 isclosed, the control relay RY4 coil (pins 2 to 7) is deenergized, theN.C. contacts (pins 8 to 5) are closed and the “AMPULE NOT FILLING”indicator LED7 is on, the N.O. contacts (pins 8 to 6) are open and the“AMPULE REFILLING” indicator LED6 is off, the N.O. contacts (pins 8 to6) are open and the N.C. coil of air control valve V2 is deenergized,and solenoid valve 12 is closed. When the N.C. solenoid valve V2 isclosed, there is no control pressure supplied to pneumatic valve 42through passage 43.

To start the refill cycle, the “PUSH TO FILL” switch SW2 is momentarilypushed closed, the coil of control relay RY4 (pins 2 to 7) is energizedthrough the N.C. contacts of SW3, RY1 (pins 1 to 4), RY2 (pins 1 to 4),RY3 (pins 1 to 4). As RY4 energizes, N.O. contacts (pins 1 to 3) close.This energizes relay RY4 and latches it in the energized state. “PUSH TOFILL” switch SW2 may now be released.

The refill cycle continues with RY4 energized, the N.C. contacts (pins 8to 5) are open and the “AMPULE NOT FILLING” indicator LED7 is turnedOFF. Also, the N.O. contacts (pins 8 to 6) are closed, and the “AMPULEREFILLING” indicator LED6 is turned on. Finally, the N.O. contacts (pins8 to 6) are closed and the N.C. solenoid valve V2 is energized and thevalve is opened. When the N.C. solenoid valve V2 is opened, controlpressure is supplied through passage 43 to pneumatic valve 42, openingpneumatic valve 42. Source chemical from bulk container 20 can now flowthrough refill line 44 to ampule 30.

The end of the refill cycle occurs in one of six (6) ways:

MODE 1: Control pressure failure: Pneumatic valve 42 closes, ending therefill cycle. MODE 2: Power Failure: The N.C. solenoid valve V2 is de-energized nd solenoid valve V2 is closed. When the N.C. solenoid valveV2 is closed, no control pressure is supplied through passage 48 topneumatic valve 42. Thus, pneumatic valve 42 closes, ending the refillcycle. MODE 3: ABORT FILL: If an operator presses the “ABORT FILL”switch SW3, which is a push-button switch, the refill circuit 82 isbroken. Control relay RY4 de-energizes, N.O. contacts (pins 8 to 6)open, and N.C. solenoid valve V2 is de-energized, cutting off the flowof control pressure to pneumatic valve 42 and ending the refill cycle.MODE 4: BULK.EMPTY: If the level of product in the bulk container 20goes below the “EMPTY LEVEL” trigger point, the float of dual levelfloat sensor 24 floats down with respect to the “EMPTY LEVEL” triggerpoint, and the “BULK EMPTY” sensor read switch RS2 closes. As a result,the control relay RY1 coil (pins 2 to 7) is energized, N.C. contacts(pins 1 to 4) open, and the refill circuit 82 is broken. This causescontrol relay RY4 to de- energize, N.O. contacts (pins 8 to 6) to open,and N.C. solenoid valve V2 is de-energized, closing solenoid valve V2.When the N.C. solenoid valve V2 closes, no control pressure is suppliedthrough passage 48 to pneumatic valve 42. Thus, pneumatic valve 42closes, ending the refill cycle. MODE 5: AMPULE HIGH-HIGH: If the levelof source chemical in ampule 30 goes above the “HIGH-HIGH LEVEL” triggerpoint 41a, the float of dual level float sensor 39 floats up withrespect to the “HIGH-HIGH LEVEL” trigger point 41a, and the “HIGH-HIGH”sensor reed switch RS3 closes. In turn, the coil of control relay RY2(pins 2 to 7) is energized, the N.O. contacts (pins 8 to 6) close, andthe N.O. solenoie valve V1 is energized, closing the valve. When theN.O. solenoid valve V1 is closed, no control pressure can be suppliedthrough passage 48 to pneumatic valve 42, thus ending the refill cycle.Additionally, when relay RY2 is energized, the N.C. contacts (pins 1 to4) open, and the refill circuit 82 is broken. As a result, control relayRY4 de-energized, N.O. contacts (pins 8 to 6) open, N.C. solenoid valveV2 is de- energized, causing solenoid valve V2 to close. When N.C.solenoid valve V2 is closed, no control pressure can be supplied throughpassage 48 to pneumatic valve 42, thus ending the refill cycle. MODE 6:AMPULE HIGH: If the level of source chemical in the ampule 30 goes to orabove the “HIGH LEVEL” trigger point 41, the float of dual level floatsesnsor 39 floats up with respect to “HIGH LEVEL” trigger point 41, andthe “AMPULE HIGH” sensor reed switch RS4 closes. In turn, the coil ofcontrol relay RY3 (pins 2 to 7) is energized. When relay RY3 isenergized, the N.C. contacts (pins 1 to 4) open, and the refill circuit82 is broken. As a result, control relay RY4 deenergizes, N.O. contacts(pins 8 to 6) open, N.C. solenoid valve V2 is de-energized, causing thevalve to close. When the N.C. solenoid valve V2 is closed, no controlpressure is supplied to pneumatic valve 42, ending the refill cycle.

Sonic circuit 84 is now described in connection with FIGS. 2 and 15.When the “MAIN POWER” switch SW1 is first turned ON, the sonic circuit84 will self-test and an audible signal will be heard. The sonictransducer S1 is powered by the circuit through the N.C. contacts (pins8 to 5) of relay RY4, through the N.C. contacts (pins 8 to 5) of relayRY5, and through Diode D17. The Operator presses the “PUSH SONIC OFF”switch SW4 to silence the audible signal.

When the “PUSH SONIC OFF” switch SW4 is momentarily closed, the Controlrelay RY5 coil (pins 2 to 7) is energized. As a result, N.C. contacts(pins 8 to 5) open, and the audible signal is turned off. Also, N.O.contacts (pins 1 to 3) close. When relay RY5 is energized, N.O. contacts(pins 1 to 3) are latched “PUSH SONIC OFF” switch SW4 may now bereleased and the audible signal will stay off.

At the start of the refill cycle, control relay RY4 energizes. In turn,N.C. contacts (pins 1 to 4) and N.C. contacts (pins 8 to 5) open,de-energizing and un-latching control relay RY5 and simultaneouslyremoving power from the contacts of RY5 connected to the sonictransducer S1. Therefore, the audible signal still remains off.

At the end of the refill cycle, control relay RY4 de-energizes. Inaddition, N.C. contacts (pins 8 to 5) close and, through the N.C.contacts (pins 8 to 5) of RY5, energize the sonic transducer S1 so thata audible signal is sounded.

At the Operator's discretion, the Sonic audible signal may be silencedby pressing the “PUSH SONIC OFF” switch SW4. When SW4 momentarilycloses, control relay RY5 energizes and latches as described above. Inturn, N.C. contacts (pins 8 to 5) open and de-energize the sonictransducer S1. Also, N.O. contacts (pins 1 to 3) close, energizing andlatching relay RY5 in the energized state. “PUSH SONIC OFF” switch SW4may now be released and the audible signal will stay OFF until the nextrefill cycle ends.

When the “PUSH TO TEST INDICATORS” switch SW5 is momentarily pressed,test circuit 80 is completed and power is connected to LED1, LED2, LED3,LED 4, LED5, LED6, LED 7, and sonic transducer S1, thus energizing allof these indicators.

Each Diode anode of test circuit 80 is connected in parallel to thedirect drive Diode anode of the various indicator circuits. This blocksany potential false circuit paths.

Diodes D9, D14, D19, D20, D22, D23 are connected in parallel acrosstheir respective relay coils with their cathodes toward the positivepower supply line. When a coil that has been energized in deenergized,the magnetic field that is created, quickly collapses and creates atransient voltage of opposite polarity to the energizing voltage acrossthe coil terminals. Diodes D9, D14, D19, D20, D22, D23 provides adischarge path in its forward biased direction for this transientvoltage and dissipates the stored energy. This configuration tends toprotect the contacts of the switch that energizes the coil from highvoltage spikes that may cause arc damage and also contributes to aquieter overall electrical environment.

FIG. 16 illustrates a partial view of a chemical cabinet 69 having twomanifolds 22 therein. Each manifold 22 connects up to a separate bulkcontainer 20. Manifold 22 contains six valves: process line isolationvalve 70, carrier gas isolation valve 71, container bypass valve 72, lowpressure vent valve 73, emergency shut off valve 74, and vacuum supplyvalve 75. Obviously chemical cabinet 69 can have one or more manifoldsin it depending on process requirements.

A particularly preferred manifold arrangement is depicted in FIG. 17.The difference between the manifold in FIG. 16 and the one in FIG. 17 isthat a block valve 76 contains both a container bypass valve 72 and aprocess line isolation valve 70. Thus, bloc, valve 76 is substituted forseparate valves 70 and 72 of FIG. 16. As a result of this modification,high purity source chemical is prevented from being trapped in thepassage 89 of refill line 44 illustrated in FIG. 16. This is becausepassage 89 is effectively removed from the manifold with the use ofblock valve 76. Thus, the manifold configuration of FIG. 17 furtherreduces the risk of introducing contamination to the system.

A most preferred embodiment of manifold 22 is depicted in FIG. 18. Inthis embodiment, in addition to employing a process isolation blockvalve 76 for the canister bypass valve 72 and the process line isolationvalve 70, a vacuum/pressure block valve 91 is used for the low pressurevent valve 73 and the carrier gas isolation valve 71. Again, as with theembodiment depicted in FIG. 17, the basic operation of the manifolds arethe same. Thus, the description of the operation of the manifold forvarious processes applies to all three depicted embodiments.

Manifold 22 is preferably used to isolate the refill line 44 when thebulk container 20 is replaced with a fresh tank. This helps preventcontamination of the system. Thus, the preferred manifold 22, is notrequired for operation of refill system 18. Naturally, if a manifold isnot used, bulk canister inlet valve 64 will need to be attached to aregulated source of inert gas and bulk canister outlet valve 66 willneed to be connected to refill line 44.

Process line isolation valve 70 is interposed in refill line 44 betweenthe inlet valve 38 of ampule 30 and the outlet valve 66 of bulkcontainer 20. When process line isolation valve 70 is closed, theportion of process line 44 down stream from valve 70 is isolated fromthe atmosphere during subsequent replacement of bulk tank 20. Carriergas isolation valve 71 is interposed in carrier gas line 77 between theinlet valve 64 of bulk container 20 and the carrier gas supply source.

Low pressure vent valve 73 is interposed in vacuum line 78, which iscommunicated to both the carrier gas line 77 and refill line 44.Container bypass valve 72, however, is interposed in the line betweenrefill line 44 and low pressure valve 73. This line is both pressurizedor evacuated dependent on the states of LPV and CGI.

Emergency shut off valve 74 is a normally closed valve, preferably apneumatic valve. Thus, any loss in system air pressure will immediatelyclose the valve. Typically emergency shut off valve 74 is controlled bythe facility emergency gas pad shut off control system. The use ofpneumatically activated normally closed valves in the manifold and onthe bulk canister inlet and outlet enables all valves to act asemergency shut-off valves. Thus, when the ESO condition is activated,the pneumatic supply to the valves will be cut off, closing all valves.Vacuum supply valve 75 is disposed in a venturi loop 99 so that when itis opened, vacuum is supplied to vacuum supply lines 78.

During normal operation the manifold 22 is left in the deliveryconfiguration. Pneumatic valve 42 in the refill line 44 is used tocontrol the refilling operation. In the delivery configuration theemergency shutoff valve 74 is open, the carrier gas isolation valve 71is open, the process line isolation valve 70 is open, the vacuum gasshutoff valve 75 is closed, the low pressure vent valve 73 is closed,the canister bypass valve 72 is closed, the bulk canister inlet valve 64is open and the bulk canister outlet valve 66 is open.

To change the bulk canister 20, the following preferred procedure isused to prevent contamination of the high purity chemical beingdelivered. First the high purity chemical must be evacuated from themanifold and the bulk canister 20 depressurized and isolated. Next themanifold should be purged. After purging, the depleted bulk canistershould be disconnected and removed. Then the new full bulk canister 20should be installed and connected. The connections for the full bulkcanister should be tested for leaks. The manifold should then be purgedand the new bulk canister 20 placed in service.

To evacuate the high purity chemical remaining in the manifold 22 and toisolate, depressurize and shut off the bulk canister 20, the followingprocedure is presently preferred. (It should be noted that unlessotherwise expressly noted, the emergency shutoff valve 74 should open bethroughout all of the following procedures.) Ensure that the containerbypass valve 72 is closed, which it should be in the deliveryconfiguration. Then close the process line isolation valve 70. Nextclose the bulk canister outlet valve 66. Close the carrier gas isolationvalve 71 and open the vacuum gas shutoff valve 75 and the low pressurevent valve 73. Wait until the manifold pressure gauge 92 readsapproximately zero psia, which takes approximately four minutes. Closethe bulk canister inlet valve 64. Close the low pressure vent valve 73and open the carrier gas isolation valve 71 and the canister bypassvalve 72. Open the canister outlet valve 66 and wait approximately ahalf a minute or until the bulk canister pressure equalizes with thepressurizing gas. Close the bulk container bypass valve 72, the bulkcanister outlet valve 66 and the carrier gas isolation valve 71. Openthe bulk canister inlet valve 64. The foregoing steps should preferablybe repeated a number of times, most preferably a minimum of five times.Finally the bulk canister inlet valve 64 should be closed.

To purge the manifold prior to disconnecting the depleted canister 20,the following steps should preferably be followed. Open the canisterbypass valve 72 and the low pressure vent valve 73. Wait approximately30 seconds to maximize the evaporation of the residual high puritychemical in the manifold. Close the low pressure vent valve 73 and openthe carrier gas isolation valve 71. Wait approximately 4 seconds andthen close the carrier gas isolation valve 71. Open the low pressurevent valve for approximately 10 seconds and then close it again. Repeatthe steps of closing the low pressure vent valve 73; opening the carriergas isolation valve 71; waiting approximately 4 seconds and then closingthe carrier gas isolation valve 71; and, opening the low pressure ventvalve for approximately 10 seconds and then closing it again preferablya minimum of nineteen times. Then close the vacuum gas shutoff valve 75and wait approximately three seconds. Then open the low pressure ventvalve 73 for approximately five seconds.

To disconnect and remove the depleted bulk canister 20, the followingsteps are preferred. Open the carrier gas isolation valve 71 to keep apositive pressure of the pressurizing gas, preferably helium, on themanifold. Open the canister inlet and outlet valves 64 and 66. With asuitable tool, support the canister outlet valve 66 to prevent rotation,and then loosen the canister outlet valve 66 connection and disconnectthe canister outlet tubing 79. In a similar fashion, disconnect thecanister inlet tubing 88. The pressurizing gas should be flowing freelyout of the canister inlet and outlet tubing 88 and 79 throughout theoperation and until the new canister is connected. This preventsatmospheric contamination of the manifold. Disconnect the level sensorcable, unfasten the safety chains and straps and carefully remove thedepleted bulk canister 20 from the enclosure.

A presently preferred method of disconnecting the depleted bulkcontainer 20 consists of the following steps. Open the carrier gasisolation valve 71 to keep a positive pressure of the pressurizing gas,preferably helium, on the material. With a suitable tool, support thecontainer outlet valve 66 to prevent rotation, and then loosen thecontainer outlet valve 66 connection and disconnect the container outlettubing 79. In a similar fashion, disconnect the container inlet tubing88. The pressurizing gas should be flowing freely out of the containerinlet and outlet tubing 88 and 79 throughout the operation and until thenew container is connected to prevent contamination of the manifold.Disconnect the level sensor cable, unfasten the safety chains andstraps, and carefully remove the depleted bulk container 20 from theenclosure.

To install a full bulk canister 20, the following steps shouldpreferably be performed. Carefully place the bulk canister in theenclosure and reconnect the safety strap and chain. Connect the canisterinlet valve 64 and outlet valve 66 connections to the inlet and outlettubing 88 and 79 reversing the procedure used to disconnect them fromthe depleted bulk canister 20. Connect the level sensor cable and closethe carrier gas isolation valve 71.

Before moving to the next step, a test for leakage should be performed.Open the vacuum gas shutoff valve 75 and the low pressure vent valve 73.After approximately 10 seconds, close the low pressure vent valve 73 andopen the carrier gas isolation valve 71. After a few seconds, preferablyfour, close the carrier gas isolation valve 71 and the vacuum gasshutoff valve 75. Using an appropriate leak tester, check the inlet andoutlet canister connections for leaks. If none appear, the manifoldshould be purged and then set for normal operation.

To purge the manifold, with the canister inlet and outlet valves 64 and66 closed, the canister bypass valve 72, the vacuum gas shutoff valve 75and the low pressure vent valve 73 should first be opened. The canisterbypass valve 72 should already be open as a result of the purge sequenceconducted before disconnecting depleted bulk container 20. Afterapproximately 10 seconds, the low pressure vent valve 73 should beclosed. Open the carrier gas isolation valve 71 for approximately fourseconds and then close it. Repeat the opening and closing of the lowpressure vent valve 73 and the carrier gas isolation valve 71 preferablya minimum of nineteen times. Open the low pressure vent valve 73 forapproximately 15 seconds to ensure that vacuum has been pulled on themanifold and then close it. Close the vacuum gas shutoff valve 75 andthe canister bypass valve 72.

To place the manifold 22 in the normal operating configuration, slowlyopen the carrier gas isolation valve 71. Then slowly open the canisterinlet valve 64 and then the canister outlet valve 66. Adjust thepressure regulator to the desired delivery pressure and open the processline isolation valve 70.

In addition, the manifold 22 can be used to purge and evacuate therefill line 44 as well. To accomplish this, the purge and evacuationcycles would be performed with the process line isolation valve open andthe pneumatic valve 42 closed. Also, if desired, additional parts of thesystem can be evacuated and purged by merely opening downstream valvesto the final point that is desired to be purged. The suggested times forpurging and evacuating should be extended to allow for the vacuum to becompletely pulled on the lines being evacuated and purged.

While the bulk chemical refill system of the present invention has beendescribed in connection with high purity TEOS, the system hasapplication with many other high purity source chemicals, as a person ofordinary skill in the art would recognize. A non-exclusive list of thevarious high purity chemicals that might be used in the chemical refillsystem of the present invention is contained in Table 1.

TABLE 1 Aluminum Tri-sec-Butoxide Borazine Carbon TetrachlorideTrichloroethane (TCA) Chloroform Trimethylphosphite (TMP)Dichloroethylene (DCE) Trimethylborate (TMB) Dichloromethane (DCM)Titanium N-Butoxide Diethylsilane (DES) Titanium IsopropoxideHexafluoroacetylacetonate- Tantalum Ethoxide Copper(I)-Trimethylphosphine Silicon Tetrachloride Triethylborate (TEB)Tetrakis (Diethylamino) Triethylphosphate (TEPO) Titanium (TEAT)Triethylphosphite (TEP) Trimethylphosphate (TMPO) Titanium TetrachlorideTitanium Ethoxide Triethoxyfluorosilane (FTEOS) Titanium IsobutoxideTrimethylorthosilicate (TMOS) Titanium N-propoxideTetramethylcyclotetrasiloxane Tris (Trimethylsiloxy) Boron (TTMSB) Tris(Trimethylsilyl) Phosphate (TTMSP)

Now a particularly preferred use of a digital level sensor assembly 21will be described in connection with FIGS. 19, 20 and 20 a.

FIG. 19 illustrates a rectangular ampule 100 of a configurationtypically used in Applied Materials' P5000 CVD platforms for deliveringTMB, TMP, TEPO or TEB dopants to a Plasma Enhanced Chemical VaporDeposition (PECVD) reactor. The Applied Materials' P5000 CVD platformhas two primary process types: (1) PECVD and (2) Sub-AtmosphericChemical Vapor Deposition (SACVD). These processes utilize the samemainframe and chemical delivery platforms, although the exactconfiguration of the valves and piping on ampule 100 varies slightlybetween the two process types depending on the source chemical to bedelivered to the CVD reaction chamber.

Rectangular ampule 100 is designed and manufactured to enable placementof seven ampules 100 in close proximity to the CVD reaction chamber.Rectangular ampules 100 are enclosed in a single “oven” type temperaturecontroller, or hot box, that houses the ampules and the downstreamhardware for flow control, purging, and liquid and particle control.

Rectangular ampule 100 illustrated in FIG. 19 is for delivering dopantssuch as TMB or TMP to a PECVD reaction chamber because it only has asingle outlet/inlet valve 102. Pneumatic purge valve 103 in purge line105 is merely for purging the delivery line 32. Earlier models ofrectangular ampule 100 did not have this purge feature. The need topurge the delivery line 32 from a point of shutoff on the ampule back tothe chamber was needed so that the low levels of chemicals with pungentodors, e.g., TMB and TMP, could be more completely removed.

Only a single valve is needed for delivery of dopants such as TMB or TMPto the PECVD reaction chamber because the standard dopants for PECVDtype reactors are delivered to the reaction chamber simply by flowingvapor from above the liquid in the ampule. This is possible because theprocess flow rates required for some dopants, such as TMB and TMP, aremuch lower than that required by, for example, TEOS. Further, the vaporpressure of these dopants is much higher than that for TEOS. As aresult, pressurized delivery of the source chemical is not required aswith TEOS. When a purge style dopant rectangular ampule 100 such as theone in FIG. 19 is used, it cannot be refilled without removing it fromthe CVD processing equipment and sending it to a chemical supply companyfor cleaning and refilling.

When TEOS is the desired chemical to be delivered to the CVD reactionchamber, rectangular ampule 100 is provided with three valves, a manualvalve for the carrier gas introduction, a manual valve for permittingthe TEOS vapor out of the rectangular ampule 100 and into delivery line32, and a pneumatic inlet valve 116 for performing frequent refills froma remote bulk chemical source container.

The three valve configuration for rectangular ampule 100, shown in FIG.20a is also used when delivering dopants such as B and P in SACVDreactors. As the name implies, the SACVD process is run just belowatmospheric pressure at about 600 torr. Due to this high pressure, the Band P dopants for the SACVD process, for example TEB and TEPO alsorequire carrier gas type delivery to the reaction chamber. Thus, themanual valve for the carrier gas introduction and manual valve forpermitting the dopant vapor out of the rectangular ampule 100 and intodelivery line 32 are used in this application.

In each of the various configurations of rectangular ampule 100, acapacitive sensor 104 mounted to lid 101 is currently used to monitorthe fluid level within rectangular ampule 100. Capacitive sensor 104provides a continuous level output from the rectangular ampule becausethe output of capacitance sensor 104 continuously changes as the fluidlevel changes within rectangular ampule 100. Currently when a presetcapacitance is measured corresponding to a low trigger point thedepleted rectangular ampule 100 is simply replaced with a full ampulewhen it contained the B or P dopant. If the rectangular ampule 100contained TEOS, on the other hand, then the ampule may be refilled untilthe output of the capacitance sensor 104 reached a preset trigger pointcorresponding to a full ampule. The trigger points were set such thatthe TEOS level is maintained at the center of the sight glass 106, whichcorresponds to approximately 475 ml of TEOS, which is considered to be100%. The volume of TEOS is preferably maintained at this softwareprogrammed 100% level. The refill sequence is typically requested whenthe level of source chemical reaches 98%, but refilling will not bebegun until the wafers currently in process are completed and a wafertransfer is performed. At that time the TEOS refill is accomplished.Typically the refilling continues until the level in rectangular ampule100 reaches 102% of the software programmed level or a 10 second timeouthas elapsed. Current TEOS refill systems for the P5000 system is set upin this manner to maintain the temperature of the TEOS in the ampule asstable as possible and to avoid additional downtime due to overfillsfills or container changes as was previously practiced. A consistentlevel of TEOS is desired to provide as much consistency in TEOSsaturation as possible. This results in a more repeatable process, waferto wafer and lot to lot. Unfortunately, due to the problems with therepeatability of the level sensing of capacitance probe, the TEOS refillsystem was not completely reliable. For example, with the capacitanceprobe 104 one could not always be sure that the output of the probe 104would be the same for 102% or 98%.

To overcome problems of capacitive sensor 104, the present inventioncomprises a digital level sensor assembly 21 which is directlysubstituted for capacitive sensor 104. As illustrated in FIG. 20,digital level sensor assembly 21 has been configured to mount in thesame location as the capacitive sensor 104. The use of the a digitallevel sensor improves the reliability of the sensor, the repeatabilityof the sensor, simplifies the construction of rectangular ampule 100,and reduces or eliminates leak integrity issues, thus renderingrectangular ampules safer to work with for chemical suppliers cleaningand refilling rectangular ampule 100 and for workers handling therectangular ampules in the field.

Although FIG. 20 illustrates a preferred form of a digital sensor, adigital metallic float level sensor assembly, substituted for acapacitive sensor 104 in a rectangular ampule 100 having a single valveconfiguration with purge capabilities, digital sensors can besubstituted for capacitance probes used in all the variousconfigurations of rectangular ampule 100. For example, FIG. 20aillustrates a rectangular ampule 100 having a three valve configurationfor delivery of TEOS that has been improved by the replacement ofcapacitive sensor 104 with digital metallic float level sensor assembly21.

The use of a digital level sensor assembly for level sensing inrectangular ampules 100 is particularly preferred when the sourcechemical to be delivered is TMB or TMP, as is the case with theembodiment illustrated in FIG. 20. This is because these dopantmaterials experience more problems both from the leak integritystandpoint and from an accuracy and repeatability standpoint.

Digital level sensor assembly 21 is attached to rectangular ampule 100by way of flange 110. Flange 110 is permanently attached to one end ofshaft 28. Flange 110 is preferably constructed out of 315L stainlesssteel, and the preferred method of attachment is welding. The holepattern for attaching flange 110 to lid 101 of rectangular ampule 100 isthe same as that found in the attachment flange 108 on capacitive sensor104. Thus, digital metallic level sensor assembly 21 can be screweddirectly to lid 101 of rectangular ampule 100 using existing attachmentpoints. To ensure good leak integrity, an O-ring 107 is fitted intogland 111 located on the mating surface 113 of flange 110 so that asflange 110 is screwed down to lid 101, O-ring 107 will be compressedbetween the mating surface 113 of flange 110 and the mating surface oflid 101. This is the same type of “face seal” O-ring that is used withcapacitive sensor 104. However, the need for the two O-rings that areused to seal and ensure the electrical separation of the two capacitivesurfaces of sensor 104 is eliminated with the present invention. It isthese O-rings, as indicated above, that are responsible for leakintegrity problems. Thus, leak integrity problems are eliminated orsignificantly reduced with the design of the present invention.

To prevent contamination of the high purity source chemical containedwithin rectangular ampule 100, the wetted surfaces of metallic levelsensor assembly 21, which comprises shaft 28, metallic float 24,retainer ring 27 and flange 110, are preferably electropolishedfollowing assembly. The surface finish of the wetted metal parts ispreferably Ra 20 or better prior to electropolishing.

Digital level sensor assembly 21 in FIGS. 20 and 20a comprises a singlemetallic level sensor 39. Preferably metallic level sensor 39 is a duallevel sensor employing two digital magnetic reed relay switches in themanner described above in connection with FIGS. 4-6 and 9-12. Triggerpoints 115, 115 a of metallic level sensor 39 preferably correspond to20% source chemical remaining (“Low”) and 5% source chemical remaining(“Empty”) in rectangular ampule 100, respectively. Because metalliclevel sensor 39 is a dual level sensor, four wires are used in cable 35to communicate the fluid level status within rectangular ampule 100.

The rectangular ampule 100 of the embodiment in FIG. 20 is notrefillable without disconnection from the system. Thus, it is simplyremoved and replaced when the “Empty” trigger point alarm is tripped andreplaced with a full rectangular ampule 100.

A dual level metallic level sensor 39 can interface directly with thelow level monitor 120 illustrated in FIGS. 21 and 22 via cable 35. Lowlevel monitor 120 provides independent level alarms with or withoutcommunication with the CVD process equipment. Specifically when metallicfloat 24 is above trigger points 115 and 115 a, the “LEVEL STATUS OK”indicator will be lit on display panel 122. When metallic float 24 dropsbelow trigger point 115, but is above trigger point 115 a, the “LOW”indicator light will turn on. And, when metallic float 24 finally dropsbelow trigger point 115 a, the “EMPTY” indicator light will turn on. Anaudible alarm in low level monitor 120 is also activated when metallicfloat 24 drops below trigger point 115 a or if communication with thedigital sensor is disrupted. The preferred circuit for effecting theoperation of low level monitor 120 is shown in FIG. 22. Cable 35 isconnected at the terminals indicated as RSW 1 and RSW 2. The symbol RYin FIG. 22 indicates a relay and the remaining elements are shown usingstandard electrical symbology.

As discussed above, FIG. 20a depicts a non-refill configuration andrequires that the rectangular ampule 100 be removed from the system onceit is nearly empty for cleaning and refilling.

The benefits to be gained from this configuration include reliable levelsensing, enhanced ability to plan container changes and thereby preventthe ampule from running empty and zeroing out product wafers during arun. Instead of replacing the rectangular ampule with 200 to 250 gramsremaining, rectangular ampules 100 can now be replaced when only 125 to150 grams source chemical remaining. Savings is achieved not only inreduced chemical cost, but also from less frequent downtime due toampule changeover and whatever associated equipment issues that mayresult. Less frequent replacement also means less frequent handling,shipping and freight expenses for containers and less manpower inseveral departments. Moreover, due to the enhanced leak integrity of therectangular ampules 100 modified to include the digital sensor, safetyis less of a concern during ampule replacement.

Moreover, as a result of the less frequent ampule changes, a number ofthe issues that arise when completing an ampule changeover in a systemthat has a temperature controlled ampule, such as the P5000, areminimized. For example, as a result of the less frequent ampulechangeover, the ampule needs time to cool down to a reasonabletemperature prior to initiating the removal process. There may be a 3 to24 hour process to properly purge the manifold and change the ampulebecause the full ampule needs to heat up to set point temperature(38-48° C.), which can take a significant period of time due to the massof the ampule. And, the process does not always come back intospecification upon start-up after an ampule change. So, overall, thereare a fair number of disadvantages to physically changing therectangular ampule 100. But these problems are all minimized whencapacitive sensor 104 is replaced with digital level sensor assembly 21.

If digital level sensor assembly 21 is only a single low level sensor,low level monitor 120 can still be used. Low level monitor 21 acceptssix inputs, two for RSW 1, two for RSW 2 and two for communication asillustrated in FIG. 22. By jumping the sensor inputs for the “LOW” and“EMPTY” circuits together, when the single sensor closes, the input pinsfor both the “LOW” and “EMPTY” circuits will be closed by the samesensor and both LEDs in low level monitor 120 will illuminate and therespective relays will energize.

In a similar manner, low level monitor 120 as described above inconnection with rectangular ampule 100, can also be used with the ampuleconfigurations described above in connection with FIGS. 8-10 and inconjunction with bulk container 20.

Low level monitor 120 can also be used as a tool interface tocommunicate the level of fluid in rectangular ampule 100, with the CVDprocessing equipment. Dry contact outputs are provided for “ContainerLow”, “Container Empty” and fault alarms. Outputs are fuse protected toprevent damage in the event of external power overload.

A preferred interface circuit is shown as low level monitor interface130 for communicating the output signals from low level monitor 120 tothe Applied Materials' P5000 is illustrated in FIG. 23. This circuitcould be employed with the digital metallic level sensor assembly 21configuration illustrated in FIGS. 20 and 20a. The inputs 1 through 9 oflow level monitor interface 130 correspond to the similarly labeledoutputs on FIG. 22.

Low level monitor interface 130 provides and interface between therelays of the low level monitor 120 to directly interface with the P5000electronics. Low level monitor interface 130 preferably outputs 10 voltswhen both sensors are floating, 4.0 volts when the low level relay istoggled and 2.0 volts when the empty relay toggles.

The use of both the N.O. and N.C. contacts of relays RY1, RY3, and RY7in the low level monitor circuit of FIG. 23 provides the switchingcapabilities so that each trigger level can be converted to an analogsignal without additional relays or circuitry being required. Low levelmonitor interface 130 is easily installed and is unique in that it cansimply replace the existing level sensor interface board. The benefit tothe user of this system is that the operator or engineer running theequipment does not have to monitor an independent monitoring systembecause the low and empty levels will also be displayed on the screen ofthe CVD equipment such as the P5000. Again, in this non-refillapplication depicted in FIG. 20 the rectangular ampule 100 must bereplaced after the “Empty” alarm is triggered.

FIGS. 24-28 illustrate alternative embodiments of digital level sensorassemblies 21 for use in rectangular ampule 100 and the correspondingpreferred circuitry for interfacing the signal from the metallic floatlevel sensor 39 with the electronics of the P5000.

In FIG. 24, the five level digital level sensor assembly 132 comprises asingle metallic float level sensor 39. Metallic float level sensor 39,however, has five trigger points corresponding to the placement of fiveN.O. magnetic reed switches RS within hollow shaft 28; thus, themetallic level sensor 39 can detect five different fluid levels.Preferably reed switches RS are configured within shaft 28 to detectfluid levels of 100%, 80%, 60%, 40%, and 20%. As illustrated in FIG. 24,this means that for a rectangular ampule 100 that is to be used in aP5000 system, a reed switch should be positioned at 0.75 in., 1.538 in.,2.326 in. 3.114 in., and 3.9 in. below the bottom surface of flange 110of metallic level sensor assembly 21. The five reed switches RS in thisconfiguration utilize a common ground. Therefore, cable 35 contains sixwires 25, one common and five returns.

Preferably the five level digital metallic float level assembly 132 isinterfaced with the P5000 electronics via five level single floatinterface circuit 131 illustrated in FIG. 25. The five level singlefloat interface circuit 131 communicates directly with the P5000electronics and will provide an analog signal corresponding to theapproximate chemical level in the ampule. The output of interfacecircuit 131 to the P5000 is preferably 10.0 volts, 8.0 volts, 6.0 volts,4.0 volts, and 2.0 volts when the reed switches corresponding to the100%, 80%, 60%, 40%, and 20% trigger points are triggered, respectively.

Again, in a non-refill application, rectangular ampule 100 will requirereplacement with a full ampule once the trigger point corresponding to“Empty” has been triggered, which would be the 20% trigger point in thisconfiguration.

The benefit of using the digital metallic level sensor assembly 132 ofFIG. 24 in combination with rectangular ampule 100 is that the user willbe provided more than just a low and empty signal, which is the case forthe metallic level sensor assembly 21 illustrates in FIG. 20. Indeed,with digital level sensor 132, the level will be displayed from 100%down to 20% resulting in a more desired output for the user.

FIG. 26 illustrates a two float five level digital metallic level sensorassembly 133 for use in a rectangular ampule 100 comprising two digitalmetallic level sensors 39. The upper digital metallic sensor 116 is adual level sensor, and the lower digital metallic sensor 117 is a threelevel sensor. Thus, metallic level sensor assembly 21 can detect a totalof five levels. The five trigger points of digital level sensor assembly133 are located in the same position as those for digital level sensorassembly 132 illustrated in FIG. 24. The five N.O. reed switches RS inthis configuration use a common ground. As a result, cable 35 containssix wires, one common and five returns.

An advantage of this configuration is that in a power down situation, atleast one of the two sensors will be on a reed switch when the systemcomes back on line due to the selective placement of retainer rings 27,which may comprise an O-ring, on shaft 28. Thus, the P5000 is providedwith an output signal when the system resumes operation. The levelindicated, however, may not be completely accurate because the chemicallevel may be below the triggered reed switch, but at least it doesprovide the board with a starting point rather than a no voltage outputif no reed switch is triggered.

A five level digital metallic level sensor assembly 21 can be producedwith various combinations of digital metallic level sensors 39 havingone, two, three, or four trigger points. For example, the digital levelsensor assembly 21 can comprise three metallic level sensors 39, one atwo level sensor, the second a one level sensor, and the third a twolevel sensor. For each additional metallic float 24 that is added to themetallic level sensor assembly 21, the five level interface circuit 131in FIG. 24 is simplified. A relay is required for each non-latching reedswitch. If a float's movement stops on a reed (and stays latched once ithas been triggered), a relay is not needed in the circuit.

FIG. 27 illustrates a five level five float digital level sensorassembly 134 comprising five metallic float level sensors 39. Eachmetallic float level sensor 39 is a single level detector. However, dueto their arrangement on shaft 28, by using retainer rings 27, metallicfloat level sensor assembly 21 can detect five different fluid levels inrectangular ampule 100. The preferred levels of detection are the sameas those for the metallic level sensor assemblies illustrated in FIGS.24 and 26. There are six wires in cable 35, one common and five returns.Thus, the five magnetic reed switches located within shaft 28 and usedto set the trigger points share a common.

The magnetic reed switches used in this embodiment are N.O. switches.Thus, when rectangular ampule 100 is full, each of the metallic floats24 are floated up above its corresponding reed switch so that the N.O.reed switch is open. The metallic float 24 used in the 100% metallicfloat level sensor has the upper reed switch already latched for thestandard fill weight of chemical. This reed switch remains closed asadditional source chemical is removed from rectangular ampule 100because retainer ring 27 prevents the metallic float 24 corresponding tothe 100% level from dropping below the trigger point. This occurs foreach of the successive metallic float level sensors 39 until the lastmetallic float 24 passes its trigger point and the corresponding reedswitch is closed. At which point rectangular ampule 100 is empty.

The preferred digital to analog interface circuit 134 for interfacingthe output of digital level sensor assembly 135 with the electronics ofthe P5000 is shown in FIG. 28. The five level five float interfacecircuit 134 is very simple, inexpensive, and reliable. Further, in thecase of a power loss to the system, the level of chemical will be knownin all situations when the system comes back on line. The output voltageof circuit 130 is 10 V, 8.0 V, 6.0 V, 4.0 V, 2.0 V when the system is100%, 80%, 60%, 40%, and 20% full, respectively. When the last reedswitch, the 20% reed switch, is toggled, the rectangular ampule is emptyand the output of interface circuit 130 is 2.0 V. In the non-refillapplication, the rectangular ampule 100 must be removed and replacedwith a full ampule when this output is received by the P5000.

The interface circuits in FIGS. 25 and 28 can be modified to provide alow and empty signal to the low level monitor 120 in addition toproviding an analog signal to the P5000. This provides the user with anadditional level monitor, which can be mounted in a different locationto make certain that the status of source chemical in the ampule isknown at all times.

The embodiments of the present invention in connection with FIGS. 20-28have all been described for the non-refill, e.g., stand alone,configuration. In other words, when an empty alarm is provided,rectangular ampule 100 must be removed from the CVD processing equipmentand replaced with a full ampule. Refills from a remote bulk container,however, offer considerable advantages over the nonrefill configurationsof the present invention discussed in connection with FIGS. 20-28 above.The downtime would be reduced to the time to complete the refill and forthe temperature of the liquid to reach a set point. That time should bevery short considering that only approximately 1 pound of dopant isadded to a 25 pound ampule already at the set point in the automaticrefill configurations of the present invention. The CVD processvariations will be negligible since there are no delivery lines exposedto air or moisture, nor are there any major disruptions with thedelivery system as a whole.

To convert the dopant ampules of FIG. 20 to a refill system, a refillport must be added. It is, however, not recommended to modify lid 101 ofexisting rectangular ampules 100 with an additional port and valvewithout the ability to electropolish the weld. The electropolishprovides a passivated surface that is higher in chromium and iron oxidesand prevents interaction of the source chemicals with the stainlesssteel surfaces of the rectangular ampule 100. If a second electroplishis attempted after addition of the refill valve, the surface will becomevery rough and course and the integrity of the passivated coating iscompromised. As a result, undesirable concentrations of contaminantswould be introduced into the high purity source chemical delivered fromthe rectangular ampule 100. For that reason, additional ports cannot beadded to rectangular ampule 100. Further, placing a high purity sourcechemical in contact with an un-electropolished stainless steel surfaceis not recommended, especially for dopant materials, due to the dangerof introducing metal contamination.

To upgrade rectangular ampules 100 so that they can be used in bulkrefill applications the lid 101 can be modified to include three valvessuch as the one illustrated in FIG. 20a. However, this alternative isvery costly. The current cost of upgrading rectangular ampule 100 with athree valve lid is estimated to be between $6,000 and $10,000 perrectangular ampule 100. Accordingly, a low cost and reliable means foradapting a single valve rectangular ampule 100 for bulk refill systemsis needed. FIG. 29 illustrates such a means.

The refill digital level sensor assembly 321 in FIG. 29 has been adaptedto accommodate a refill port and inlet valve assembly 112. The refillport and inlet valve assembly 112 is preferably attached to flange 110of refill digital level sensor assembly 321 by welding. Flange 110 isthe same size as flange 108 of capacitive sensor 104 and a seal betweenthe lid 101 and the ampule 100 is preferably accomplished in the samemanner. A similar modification of the capacitance probe sensor is notpractical due to the size of the probe.

In the embodiment in FIG. 29, refill digital level sensor assembly 321comprises two metallic float level sensors 39. The first 116 is a duallevel sensor, and the second 117 is a three level sensor. Thus, as withthe level sensor assembly depicted in FIG. 26, the refill digital levelsensor assembly 321 depicted in FIG. 29 can detect a total of fivelevels. The five trigger points of refill digital level sensor assembly321 are preferably located in the same positions as those for the levelsensor assemblies 21 illustrated in FIGS. 24 and 26. And, as with thoseembodiments of the level sensor assembly 21, preferably the five reedswitches RS making up the trigger points are normally open and share acommon ground. As a result, cable 35 preferably contains six wires, onecommon and five returns.

Refill port and inlet valve assembly 112 in FIG. 29 comprises refillline 114 and inlet valve 118. Refill line 114 has an inlet port 119 andis preferably a ¼ inch 316L stainless steel pipe. Inlet valve 118 ispreferably a pneumatic valve so that when refill digital level sensorassembly 321 is mounted on rectangular purge style dopant ampule 100 tocreate a modified rectangular purge style dopant ampule 200, modifiedrectangular purge style dopant ampule 200 can be used in an automaticbulk refill system.

FIG. 30 illustrates one embodiment of an automatic bulk refill system218 for refilling a modified rectangular purge style dopant ampule 200supporting an Applied materials' P5000 PECVD unit with TMB, TEB, TEPO orTMP. As illustrated, the capacitive sensor 104 has been replaced with arefill digital level sensor assembly 321 that has been modified with arefill port and inlet valve assembly so that modified rectangular purgestyle dopant ampule 200 can be refilled from remote bulk container 220.It should be noted that for use in refill system 218, the modifiedrectangular purge style dopant ampule 200 will work regardless of whichmanner of modification is used to include a refill port and inlet valveassembly. It can be modified by drilling a hole and welding the port andvalve assembly to the lid of the ampule and the capacitance probereplaced with a digital probe assembly 21, it can be modified by usingthe refill digital probe assembly 321, or even a rectangular TEOS ampulewith the digital probe assembly 21 can be used.

Bulk refill system 218 comprises six main functional components in thisembodiment: a bulk container 220 located in a remote chemical cabinetwith a manifold 222; a modified rectangular purge style dopant ampule200 to supply a P5000 reaction chamber with TMB or TMP; a control unit240 to supervise and control the refill operation and to monitor thelevel of the bulk container 220 and modified rectangular purge styledopant ampule 200; a low level monitor 120 to monitor the low level inrectangular ampule 200 and interface electronics 130 to interface withthe electronics of the P5000; and an automatic purge controller 140 tostep manifold 222 through a purge cycle following the replacement ofbulk container 220.

Bulk refill system 218 operates essentially in the same manner as theembodiment illustrated in FIG. 1. However, because the source chemicalto be delivered from bulk container 220 in this embodiment is TMB or TMPa vacuum is not required to be pulled on modified rectangular purgestyle dopant ampule 200, which is located in hot box 126, before therefill cycle can be completed. A vacuum is not required with TMB and TMPbecause the dopants are vapor delivery and the ampule pressure istypically well below atmosphere.

All of the valves in this embodiment are preferably pneumatic to permitthe bulk refill system 218 to be configured for automatic refills ifdesired. The use of all pneumatic valves in manifold 222 and on bulkcontainer 220 also permits the addition of an automatic purge controller140 to the bulk refill system 218. Automatic purge controller 140 ispreferably used to step manifold 222 through the drain and purgesequence to permit bulk container 220 to be replaced. Automatic purgecontroller 140 is also preferably used to configure the manifold 222valves and bulk container 220 valves for the delivery of source dopantchemical to modified rectangular purge style dopant ampule 200 or forany other bulk chemical configuration or refill function. The operationof automatic purge controller 140 is described in more detail below. Lowlevel monitor 120 can be used in the present embodiment of bulk refillsystem 218 to monitor the chemical level in modified rectangular purgestyle dopant ampule 200 as described in connection with FIG. 21.However, as described in more detail below, low level monitor 120, whilepreferred, is not required in bulk refill system 218.

During normal process operation of refill system 218, modifiedrectangular purge style dopant ampule 200 delivers a high puritychemical dopant such as TMB or TMP to the reaction chamber of an AppliedMaterials' P5000 PECVD unit via delivery line 232. It should be notedthat outlet valve 102 on the back of rectangular ampule 200 has beenomitted from FIG. 30 for purposes of clarity. Further, modifiedrectangular purge style dopant ampule 200 need not be pressurized with adelivery gas as with a TEOS delivery system, because, as mentionedabove, TMB and TMP have a high vapor pressure and only low flow rates ofthese dopants are required to the CVD reaction chamber.

The operation of a most recently preferred embodiment of control unit240 is described in connection with FIGS. 31 and 32. It should be notedthat control unit 240 can be used in conjunction with a rectangular TEOSampule 100 as well as the modified rectangular purge style dopant ampule200. FIG. 31 illustrates a preferred configuration of control panel 252of control unit 240, and FIG. 32 illustrates the corresponding preferredelectrical circuit of control unit 240. The symbols used in FIG. 32 arestandard electrical symbols and refer to the standard electricalcomponents indicated by the symbol.

Control unit 240 includes six manual switches: an “ON/OFF” switch 150; a“RUN/ABORT” switch 151; a “TEST INDICATORS” switch 152; a “RESET SONIC”switch 153; a “PUSH TO FILL” switch 154; and an “AUTO FILL/MANUAL FILL”switch 155.

Control panel 252 includes a number of indicators to report the statusof chemical levels in bulk container 220 and modified rectangular purgestyle dopant ampule 200. The indicators include “EXTERNAL STATUS OK TOFILL” 155, “AUTO-START ACTIVE” 156, “MANUAL START ACTIVE” 157, “BULK OK”158, “BULK LOW” 159, “BULK EMPTY” 160, “CONTAINER REFILLING” 162,“CONTAINER NOT REFILLING” 161, “FILL TIME OUT” 163, “HIGH-HIGH LEVEL”164, “HIGH LEVEL” 165, and “CONTAINER NEEDS REFILL” 166.

The “ON/OFF” switch 150 turns on the main power to control unit 240 andprovides power to the control unit circuit in FIG. 32. The “RUN/ABORT”switch 151 is a manual and automatic refill function override. Whenpressed, it removes power from normally closed pneumatic control valveV2 (sown in FIG. 32), thereby causing refill control valve 242 and inletvalve 118 to close, shutting off the flow of source chemical from bulkcontainer 220. The “TEST INDICATORS” switch 152 tests all the LEDs andsonic alarm in control unit 240. The “RESET SONIC” switch 153 silencesthe sonic alarm within control unit 240 and energizes the alarm circuitwhen pressed. The “AUTO FILL/MANUAL FILL” switch 149 is preferablylocated on the back panel of control unit 240. When this switch is setin the “MANUAL FILL” position, the “MANUAL START ACTIVE” LED 157 isilluminated and the “PUSH TO FILL” switch 154 is enabled. On the otherhand, when this switch is set in the “AUTO FILL” position, the“AUTO-START ACTIVE” LED 156 is illuminated and control unit 240 isconfigured for automatic refill operation.

If the “EXTERNAL STATUS OK TO FILL” LED 155 is illuminated, the refillfunction is enabled. The “EXTERNAL STATUS OK TO FILL” LED 155 isilluminated when the contacts of an external refill controller overrideEX RY1 (shown in FIG. 32) generally located within the electronics ofsome CVD processing equipment are closed. Other devices can beinterlocked using the external status inputs. The only requirement isfor N.C. contacts. Thus, this circuit acts as an interlock to preventrefill of modified rectangular purge style dopant ampule 200 while theCVD unit is in normal operation. When the contacts of the override areopen, the refill function is disabled, and the “EXTERNAL STATUS OK TOFILL” LED 155 is extinguished. If the unit is not connected to anexternal interlock a jumper must be installed across pins 1 and 2 ofCONN 3.

During normal process operation, the level of source chemical in bulkcontainer 220 should not change. Therefore, the “BULK OK” indicator 158should remain lit. However, if the “BULK LOW” or “BULK EMPTY” indicator,159 and 160 respectively, come on during a refill cycle, theseindicators will remain illuminated until the bulk container 220 isreplaced with a full container. The operation of the level sensors inbulk container 220 is the same as that explained in connection withFIGS. 3-5 above. The bulk container 220 sensors 39 are represented inFIG. 32 as RS1 and RS2.

Control unit 240 interfaces with a digital metallic level sensorassembly 221 in bulk container 220 via cable 226. The metallic levelsensor 39 in the remote bulk container 220 has its trigger pointspreferably set at 20% remaining source chemical and at 5% remainingsource chemical. Depending on specific process requirements, however,other trigger points can be used. If the source chemical level fallsbelow the first trigger point, which typically only occurs during therefilling sequence, a visual indication of “BULK LOW” on the controlpanel 252 of control unit 240 is produced. If the source chemical levelfalls below the second trigger point, the “BULK EMPTY” visual alarm 160on control panel 252 in addition to an audible alarm S1 is sounded inconjunction with an automatic termination of the refill sequence.

Throughout normal process operation, the “CONTAINER NOT REFILLING”indicator 161 should remain on to indicate that the refill system is notin the refill mode. Because the level of high purity TMB, TMP, or otherhigh purity source chemical in modified rectangular purge style dopantampule 100 changes throughout normal process operation, the “HIGH” levelindicator 165, which is illuminated upon completion of a refill cycle,will remain illuminated until the high purity TMB, TMP, or other highpurity source chemical level in modified rectangular purge style dopantampule 200 falls below the “HIGH” trigger point of metallic level sensorassembly 221.

If the “HIGH-HIGH” indicator 164 was illuminated during the refillprocess, as with the “HIGH” indicator, the “HIGH-HIGH” indicator 164will remain on until the high purity source chemical in modifiedrectangular purge style dopant ampule 200 falls below the “HIGH-HIGH”trigger point of metallic level sensor assembly 321. In such a case, thechemical level will fall through the “HIGH” trigger region thus causingthe “HIGH” indicator to illuminate and then extinguish as describedabove.

The refill procedure is started either automatically orsemiautomatically. For control unit 240 to be used in the semiautomaticmode, the “AUTO FILL/MANUAL FILL” switch 155 must be set to the “MANUALFILL” position. In the semiautomatic mode when the indicators indicatethat the ampule needs refilling, the operator must manually depressingthe “PUSH TO FILL” switch 154 on control panel 252 of control unit 240shown in FIG. 31. In the automatic mode, the level sensor input to thecontrol unit 240 starts the refilling operation. The automatic mode maynot be applicable to all CVD reactors. In the automatic mode a timercircuit 180 is preferably included to provide a default shut-off of therefill operation if the HIGH LEVEL sensor RS 4 is not activated in apreset period of time.

Once the “PUSH TO FILL” switch is pushed in the manual mode or relay RY5 is automatically enabled in the automatic mode, the valve 242 isopened in the refill line 244 and inlet valve 118 on the back ofrectangular ampule 200 is opened. High purity TMB, TMP (or other highpurity source chemical, depending on the application) then flows intothe modified rectangular ampule 200 from the bulk container 220.Throughout the refill cycle, the “CONTAINER REFILLING” LED 162 on panel252 of control unit 240 is illuminated.

Valves 242 and 118 are preferably pneumatically activated valves. Thecontrol pressure used to open valves 242 and 118 can be nitrogen orother pressurization gas such as plant compressed dry air. The flow of acontrol pressure to valves 242 and 118 is controlled by N.O. solenoidvalve V1 and N.C. solenoid valve V2 in control unit 240.

Bulk container 220 is continuously pressurized with an inert gas such ashelium; thus, when valves 242 and 118 are opened, inert gas forces thehigh purity source chemical from bulk container 220 through refill line244 and into the modified rectangular ampule 200.

Digital level sensor assembly 321 in rectangular ampule 200 can take ona number configurations depending on how the bulk refill system 218 isto be operated. The following are particularly preferred configurationsof digital level sensor assembly 321 and the corresponding preferredmethods of operating bulk refill system 218.

In a first configuration, digital level sensor assembly 321 comprisestwo metallic float level sensors as illustrated in FIG. 29. Furthermore,the upper metallic float level sensor 116 is a dual level sensor, as inFIG. 29, used to indicate the “HIGH” and “HIGH-HIGH” levels withinmodified rectangular ampule 200. However, the lower metallic float levelsensor 117 is only a single level sensor for indicating a low levelinside modified rectangular ampule 200.

When the upper metallic float level sensor 116 is triggered, indicatingthat modified rectangular ampule 200 is full, it supplies a signal tothe control unit 240 via cable 35. In response to that signal controlunit 240 closes pneumatic valves 242 and 118 without operatorintervention. Simultaneously, control unit 240 signals an audible alarmand a visual alarm on control panel 252. If the “HIGH LEVEL” triggerpoint RS 4 of upper level sensor 116 should fail, the “HIGH-HIGH LEVEL”trigger point RS 3 of upper level sensor 116 will trigger and instructcontrol unit 240 that the modified rectangular ampule 200 is full viacable 35 by an independent circuit within control unit 240. This“HIGH-HIGH” alarm is a fail safe feature that prevents overfilling themodified rectangular ampule 200 and stops refilling in case ofelectrical failure of the “HIGH LEVEL” alarm circuit.

During normal use of the chemicals, the source chemical within modifiedrectangular ampule 200 is consumed within the reaction chamber of theCVD processing equipment. The low level metallic level sensor 117signals the control unit 240 via cable 35 when the source chemical levelwithin modified rectangular ampule 200 has reached a low level. When themagnetic reed switch RS 5 closes, the “CONTAINER NEEDS REFILLING”circuit in FIG. 32 is completed and the “CONTAINER NEEDS REFILLING” LED166 on control panel 252 of control unit 240 is illuminated. When“CONTAINER NEEDS REFILLING” LED 166 indicator light is illuminated, inthe manual mode, the operator would initiate a refill cycle at theappropriate time by depressing the “PUSH TO FILL” switch. In theautomatic mode, the system will automatically fill the modified ampule200.

A second possible configuration of digital metallic level sensorassembly 321 for use in bulk refill system 218 of FIG. 30 is nowdescribed. In this configuration, upper metallic float level sensor 116is a dual level digital sensor and functions in the same way as theprevious example. However, in this embodiment, lower metallic floatlevel sensor 117 is a dual level sensor with set points 115 and 115 acorresponding to “LOW” and “EMPTY” levels, respectively. With thisarrangement, metallic level sensor 117 preferably interfaces directlywith low level monitor 120 via cable 35 as described in connection withFIGS. 21 and 22. Low level monitor 120 indicates when the sourcechemical within modified rectangular ampule 200 drops below the “LOW”level and “EMPTY” level trigger points 115, 115 a, RSW 1 and RSW 2,(shown in FIG. 22) respectively, by illuminating the indicator on panel122 (shown in FIG. 21), which, if the system is in manual mode, informsthe operator that a manual start of bulk refill system 218 should becompleted soon. In this embodiment, the bulk refill would still beaccomplished through and controlled by control unit 240.

A third embodiment of bulk refill system 218 is now described. In thisembodiment, digital level sensor assembly 321 is identical to thedigital metallic level sensor assembly 321 described in the previousexample. Thus, upper metallic level sensor 117 has two trigger pointscorresponding to “HIGH” and “HIGH-HIGH” fluid levels within rectangularampule 100, and as before, the digital signal from these two triggerpoints is communicated to control unit 240 for refill termination.Furthermore, the “LOW” and “EMPTY” level signals of lower metallic levelsensor 117 are communicated to the low level monitor 120. In addition,however, in this embodiment, the outputs of low level monitor 120 arecommunicated to the electronics of the P5000 unit using the interfacecircuit 130 illustrated in FIG. 23. If desired, the N.O. low alarmoutput of low level monitor 120 shown in FIG. 22 can be used tointerface with the control unit 240 “CONTAINER NEEDS REFILLING” circuitRS 5. In this way, the “CONTAINER NEEDS REFILLING” LED 166 will lightwhen the “LOW” level trigger point is tripped.

The advantage that this embodiment provides is that the user will have avisible “LOW” and “EMPTY” warning on the screen of the P5000 and theP5000 will not allow further wafer processing after an “EMPTY” alarm isdetected. The “CONTAINER NEEDS REFILLING” indicator light 166 on controlpanel 252 would also be illuminated after the fluid level in modifiedrectangular ampule 200 drops below the “LOW” level to, in the manualmode, inform the operator that a refill should be conducted at the nextopportunity.

A fourth embodiment of the bulk refill system 218 is now described. Thesame digital level sensor assembly configuration 321 as used in theprevious two embodiments is also used in this embodiment. The outputs ofthe five trigger points are communicated directly to the electronics ofthe P5000 using the interface circuit similar that depicted in FIG. 25,except that the 60% relay may be omitted. Thus, an independent controlunit 240 and low level monitor 120 are not required in this embodiment.Rather, the P5000 electronics acts as the control unit for thisembodiment. The output signal provided by interface circuit isinterpreted by the software of the P5000 unit, which already exists forthe refill of TEOS. The software and pneumatic controls of the P5000would be modified in this embodiment to initiate a refill cycle when thefluid level drops to 20% in modified rectangular ampule 200 and to endthe refill cycle when the source chemical reaches the 80% level. Thiswould leave the 100% level as a safety “HIGH-HIGH” configuration sinceit would provide a voltage greater than the 8.0 volt set-point for the“HIGH” level.

A primary advantage to the user of this embodiment is that a separatecontrol system is not required to operate in the refill mode. Thisgreatly simplifies the installation of the bulk refill system 218.Primarily, pneumatic lines are modified such that the P5000 thinks thatit is refilling a TEOS “slot” in the hot box. In actuality the modifieddopant ampule 200 is refilling.

A fifth embodiment of bulk refill system 218 is now described. In thisembodiment digital level sensor assembly 321 is a five level sensoremploying from two to five floats such as the ones described inconnection with FIGS. 24-28. The outputs of digital level sensorassembly 321 are interfaced with the electronics of the P5000 using theappropriate interface circuit described in connection with each of theconfigurations of the digital level sensor assemblies 21 in FIGS. 24, 26or 27. An advantage of this embodiment is that incremental fills can becompleted using the P5000 software. The refill percentages of the P5000software are field programmable and can be set up to start the refillcycle at 6.0 volts and stop the refill cycle at 8.0 volts. The selectedinterface circuit will provide the analog signal change that resultsfrom the movement of the float from the 80% reed switch to the 60% reedswitch. The output is still 8.0 volts as the float approaches the 60%reed switch. Once the 60% reed closes, the ampule 200 will be refilleduntil an 80% voltage (8.0 VDC) is detected, i.e., the liquid level hasraised the float above the 60% reed switch.

If N.O. reed switches are employed, the interface circuit in FIG. 25must be modified to unlatch as the float 24 rises above the 60% reed sothat the proper signal will be sent to the P5000. The desired refilloutputs can be achieved by using a two float configuration. The upperfloat (clip ring to stop its movement) stays at the 80% R.S. and keepsit latched. As the lower float changes level on the 60% R.S., the outputwill change as the 60% R.S. latches and unlatches. Float 24 will travelapproximately ⅛ inch between trigger points, which corresponds toapproximately 30 ml source chemical per refill.

The advantage of this embodiment is that incremental refills can beperformed for added process control, repeatability, and stability duringwafer fabrication. Further, a control unit 240 independent of the CVDelectronics is not required for operation of the system.

Depending on the location, there may be a reluctance to modify the P5000to achieve the incremental fill. If so, the BRC-22A can be configured toperform the same function in the “Auto Start” mode and with the properinterface configuration chosen.

The individual reed switches in the digital level sensor assemblies canfabricated on a single PCB having a large number of reed switchesmanufactured in a line directly on the board using techniques readilyknown in the printed wiring board manufacturing art. The traces and reedswitches would be preferentially manufactured on a thin strip ofsubstrate. The reed switches can be either normally open or normallyclosed. The substrate should be thin enough to easily fit within shaft28 of the digital level sensor assembly 21. The reed switches should beevenly spaced along the length of the PCB and should be close enoughtogether so that metallic float 24 will always have at least one reedclosed. Preferably there are at least four reed switches per inch alongthe length of the PCB. This configuration will give a much more accuratelevel indication and is very close to a continuous output for the levelsof interest in the ampule.

The lowest detection level may also be improved, thus allowing for morecomplete consumption of chemical in stand alone rectangular ampules 100and modified ampules 200. For similar reasons the PCB reed switchconfiguration is also valuable in bulk refill applications due to themore accurate level indication and flexible start and stop points forthe refill process. This sensor are also preferred for the incrementalrefill configuration as well. It allows the end user more flexibility inselecting a refill level and the amount of refill.

An interface circuit for converting the trigger points is preferablyincluded on the reed switch PCB. For example the resistors of interfacecircuit shown in FIG. 25 are preferably built into the board to providea varied output for the individual reed switch. Fuzzy logic similar tothat employed in the camera arts is preferably used to determine theexact location of the metallic float 24 relative to the digital reedswitches. With the magnetic field distributed among several reeds, fuzzylogic can be used to determine the exact location of the metallic float24, and thus the fluid level. The fuzzy logic system employed ispreferably similar to the algorithms used in most advanced fullyautomatic cameras.

In this embodiment the electronics of the P5000 would be used to thecontrol the refill cycle and act as the control unit 240 for the bulkrefill system. When a preset empty condition is measured, the P5000electronics would supply a control pressure to refill valve 242 andsource chemical would begin to flow from bulk container 220 torefillable ampule 200. When the preset full condition is communicated tothe P5000 electronics, the control pressure to refill control valve 242would be cutoff and the flow of source chemical from bulk container 220to refillable ampule 200 stopped.

Chemical cabinet 269 illustrated in FIG. 30 contains one manifold 222and one bulk container 220. Chemical cabinet 269 can, however, containadditional bulk containers 220 and manifolds 222 depending upon theapplication. Manifold 222 is preferably used to isolate the refill line244 when the bulk container 220 is replaced with a fresh tank. Thishelps prevent contamination of the system.

The arrangement and basic operation of manifold 222 is identical to thatdescribed in connection with FIG. 17 above with three exceptions. In themanifold illustrated in FIG. 17, valves 70, 71, 72, 73 and 75 are manualvalves. In the present embodiment, all of the valves within manifold 222are preferably N.C. pneumatic valves. The second difference is that theemergency shut-off valve 74 has been eliminated from manifold 222 sinceall valves are now pneumatic and can be used as a shut-off. Thirdly, thepreferred manifold 222 includes a vacuum switch 370, and indicatingpressure switch 371 as required for use with the Advanced Delivery &Chemical Systems, Inc. automatic purge controller. The manifold 222 caninclude an indicating pressure transmitter (IPT) between valves 71 and73 to allow for automatic leak test functions.

The bulk canister inlet valve 264 and bulk canister outlet valve 266 arealso preferably N.C. pneumatic valves. These valves are preferablyattached directly to bulk container 220 without any manual valves, sothat when bulk container 220 is removed from the bulk system, the bulkcanister inlet and outlet valves 264, 266 remain attached to isolate theinterior of bulk container 220 from the atmosphere.

The pneumatic valves in manifold 222 and on bulk container 220 arepreferably springless diaphragm valves to minimize the particlecontamination in the bulk refill system.

Pneumatic valves are preferably used in the manifold 222 and bulkcanister 220 in this embodiment so that they can be controlled by anautomatic purge controller 140 via pneumatic control lines. Thus, thepneumatic actuators of the canister inlet and outlet valves 264, 266 andall the valves in manifold 222 are connected to individual pneumaticcontrol lines (not shown) that are in communication with the automaticpurge controller 140. As a result, automatic purge controller 140 simplycommunicates a control pressure through the appropriate pneumaticcontrol line to open a specified valve.

The line draining and purge sequences are fully automated and free ofhuman interaction if the container valves 264 and 266 are pneumatic. Ifthey are manual, a technician must be present during the line drainingprocess to open and close the canister inlet valve. To simplify themanual operation, the canister outlet valve 266, is left open during theline draining process. The CBV valve 72, is used to control that part ofthe canister.

An added benefit of using normally closed pneumatically actuated valvesin the manifold and on the bulk container inlet and outlet is that allvalves will act as an emergency shut-off valve; thus enabling theremoval of emergency shut-off valve 74 from the manifold. When theemergency shut-off condition is activated, the pneumatic supply to thevalves will be cut off, closing all valves.

The following is a preferred way to refill the bulk container havingpneumatic valves. In principle there are several very specific needs forworking with liquids especially combustible or flammable liquids. Therequirements are made even more difficult when working with theultrahigh purity levels required for the CVD, etch and diffusionapplications.

The filling process should be completed in the absence of trace moistureand oxygen. The concern raised by trace moisture and oxygen is primarilywith regards to purity and chemical stability, however, safety concernsare also present. To achieve that, the valve connections must be purgedprior to the transfer of any liquid as described above. This requirementmakes filling through the valve a distinct advantage.

Once the trace moisture and oxygen are removed down to the desired partsper million level, the actual filling process can begin. The fillingprocess is a fully automated process that utilizes pneumatic valves,analog scale outputs, a pneumatic controller and a filling manifold.Prior to filling, canister valve actuation is required to vent thepressure in the canister and to pull a vacuum on the canister. Thevacuum assists in the debubbing of CVD materials as it fills thecontainer.

After the fill process has been completed, the valves on the bulkcanister are closed automatically. The liquid between the fillingmanifold shut-off valve and the canister shut-off valve must be removedbefore the canister can be safely removed from the filling manifold.Unlike gases, the liquid must be removed out of this deadleg by pressuretransfer due to the fact that the vapor pressure of the liquid is notsufficient to remove the liquid in a time efficient manner. Theprocedure to perform that activity includes pneumatic actuation of bothcanister valves. Without the pneumatic valves on the canister, thecontainer depressurization and the final steps of the filling processwould require operator interaction and would compromise the safety andpurity considerations needed for this process.

The above process is similar to the line draining process performed bythe APC during a canister change. The needs are the same for bothprocedures.

The purpose of the automatic purge controller 140 is to perform the linedraining and purge cycle operations on the bulk canister 220 andmanifold 222. As described above in connection with FIGS. 16-18, theseoperations are quite detailed due to the need to minimize thepossibility of introducing contamination to the high purity chemicaldelivery system. By using automatic purge controller 140, the line drainand purge cycles, before and after canister change, can be optimized tovirtually eliminate the possibility of contamination and to ensure safeconditions for operators replacing the empty bulk container 220.

The operation of automatic purge controller 140 is described inconnection with FIG. 33.

Control panel 142 of automatic purge controller 140 preferably includesseven LEDs 141, one corresponding to each valve in manifold 222 and thevalves on bulk container 220. The valve abbreviations on control panel142 correspond to the valves in manifold 222 and on bulk container 220as follows: “CANISTER INLET”=canister inlet valve 264; “CANISTEROUTLET”=canister outlet valve 266; “PLI”=process line isolation valve70; “CGI”=carrier gas isolation valve 71; “CBV”=container bypass valve72; “LPV”=low pressure vent valve 73; “VGS”=vacuum supply valve 75. Whena valve LED indicator 141 is illuminated, the indicated valve is open.

Control panel 142 also includes three control switches and correspondingLED indicators 143. These are “RUN”; “PURGE”; and “STOP”. When a givenswitch is pressed, the corresponding LED indicator is illuminated. Inaddition, the automatic control unit performs the operations describedbelow.

When the run switch is pressed, automatic purge controller configuresthe valves in manifold 222 and the valves on bulk container 220 todeliver source chemical to for example modified rectangular ampule 200.As a result, carrier gas isolation valve 71, process line isolationvalve 70, canister inlet valve 264, and canister outlet valve 266 areopened. Bulk container 220 is now pressurized and will deliver sourcechemical to the modified rectangular ampule 200 when refill controlvalve 242 is opened by control unit 240 or the CVD electronics asdescribed above.

After bulk container 220 has been depleted, digital level sensorassembly 221 in bulk container 220 will signal control unit 240 viacable 226 that a “BULK EMPTY” status exists within bulk container 220.At this point, bulk container 220 will need to be replaced beforeanother refill cycle can begin, or be completed. By depressing the“PURGE” switch, automatic purge controller 140 steps the manifold andbulk container 20 through the valve control sequence described of thebulk container 20 change procedure described above in connection withFIGS. 16-18. The automatic valve controller software and truth tablesare set forth below in Tables 2-5. The display box in each tableindicates the display provided on display screen 144 of automatic purgecontroller 140 after each step of the software. The operator performingthe bulk container 220 replacement procedure must simply follow theinstructions provided on display screen 144 to effect the removal andreplacement of bulk container 220.

When the “STOP” switch is pressed, automatic purge controller 140 closesall valves in manifold 222 and on bulk container 220 by cutting of thecontrol pressure to these valves.

Preferably, automatic purge controller 140 performs the followingautomatic test functions throughout its operation.

1. Verifies the valve actuation pressure is sufficient for manifoldactuation. Adjustable pressure switch on the valve actuation sourceinput.

2. Verifies that the helium or other inert pressurizing gas is properlyregulated. Verifies a minimum delivery pressure is present at the inletof the pressurization gas.

3. Verifies that the carrier gas isolation valve 71 is functioningproperly. The vacuum switch is used to monitor leaks at the CGI valve.

4. Verifies that the low pressure vent valve 73 is functioning properly.The vacuum switch on the manifold would detect a valve failure at LPV73. A leak past LPV would be detected in the leak test process.

5. Verifies that the vacuum supply valve 75 is functioning properly. Avacuum test is performed by means of the vacuum switch on the manifold.

Further, after each bulk container changeover, automatic purgecontroller 140 also preferably performs a manifold leak check.

Preferably automatic purge controller is also configured to have a drycontact safety feature. Opening the contacts of the N.O. safety relay,stops all automatic purge controller functions. As a result all manifoldand canister valves close. In the event of a regulator failure, themechanical pressure relief valve on the regulator would vent excesspressure to the cabinet exhaust. This is an industry standard inhandling regulator failures.

TABLE 2 Liquid TEOS Draining and Canister Shutoff Can Can STEP ACTIONVGS LPV CGI PLI CBV IN OUT Display Continue 00 Open Canister Inlet I⁷Starting DRAIN and (5)01 — after VDLY SHUTOFF sequence (7)03 — afterVDLY 01 Open Canister Valves Open Canister Valves (5)02 — after PURGE ispressed Then Press PURGE 02 I⁷ I⁷ Liquid TEOS Draining (5)03 — afterVSTART Purge Cycle X of X (7)05 — after VSTART and VACUUM TEST = TRUE 03OPEN Canister INLET (5)04 — on first cycle only Then Press PURGE (5)04 —After PURGE is pressed 04 Open VGS I Starting Venturi (5)05 — afterVSTART and VACUUM TEST = TRUE 05 Open LPV I I I⁷ Depressurizing Manifold06 — after DRAIN for XXX seconds 06 Close CanIN and LPV I Closing VENTValve (5)07 — after VDLY (7)08 — after VDLY 07 CLOSE Canister INLET(5)08 — after PURGE is pressed Then Press PURGE 08 Open CGI I⁷ I OpeningPurge Valve 09 — after 2VDLY and CGI PRESSURE TEST = TRUE 09 OpenCanister Inlet* I⁷ I I I⁷ Draining Manifold and 0A — after BUBBLE Purgefor xx.x seconds 0A Close CBV, CGI, Can OUT I⁷ Closing Purge Valve 02 —after VDLY and LOOP < DRACNT (5)0A — after VDLY and LOOP = DRACNT (7)10— after VDLY and LOOP = DRACNT 0B Close Canister Valves (5)10 — afterPURGE is pressed Then Press PURGE Note: (5) means 5 valve sequence (7)means 7 valve sequence “unmarked” means common to both sequences

TABLE 3 Purging Prior to Depleted Canister Disconnection Can Can STEPACTION VGS LPV CGI PLI CBV IN OUT Display Continue 10 Open CBV, LPV I IStarting PURGE 11 — after 2VDLY and VACUUM BEFORE CANISTER TEST = TRUEEXCHANGE 11 Evaporate TEOS I I I Evacuating Manifold 12 — after VENT forXXX seconds 12 Close LPV I I Closing VENT Valve 13 — after VDLY 13 OpenCGI I I I Filling for XX 14 — after FILL Seconds Cycle X of X 14 CloseCGI I I Cycle X of X 15 — after VDLY 15 Open LPV I I I Evacuating for XX16 — after EVAC Seconds Cycle X of X 16 Close CGI I I Cycle X of X 13 —after VDLY and LOOP < CYCLE 17 — after VDLY and LOOP = CYCLE 17 CloseVGS I 18 — after 3 seconds 18 Open LPV I I 20 — after 5 seconds

TABLE 4 Purging Prior to Depleted Canister Disconnection and Removal CanCan STEP ACTION VGS LPV CGI PLI CBV IN OUT Display Continue 20 I Turn HeREG CCW 21 — after PURGE button is pressed then press PURGE 21 I I IAdjust He to 5 PSIG 22 — after PURGE button is pressed then press PURGE22 I I UNTIGHTEN 23 — after PURGE button is pressed Canister then pressPURGE 23 I I Remove EMPTY 24 — after PURGE button is pressed Canisterthen press PURGE 24 I I Install New Canister 25 — after PURGE button ispressed then press PURGE 25 I I TIGHTEN 26 — after PURGE button ispressed Connections then press PURGE 26 I Adjust He to XX 27 — afterPURGE button is pressed PSIG then press PURGE 27 Open VGS I I StartingVenturi 28 — after V_START and Vacuum Test = TRUE 28 Open LPV I I IEvacuating Manifold 29 — after EVAC for XX Seconds 29 I I Closing VentValve 2A — after VDLY 2A OPEN CGI I I Pressurizing Manifold 2B — afterFILL and Manifold Pressure Test = TRUE 2B CLOSE CGI I Leak Check 30 —after PURGE button is pressed Connections then press PURGE Leak TestingManifold 30 — after Manifold Holding Pressure for XXX sec XX.X Test =TRUE PSIG

TABLE 5 Purging After Cylinder Connection Can Can STEP ACTION VGS LPVCGI PLI CBV IN OUT Display Continue 30 Open VGS I I Starting PURGE 31 —after V_START and VACUUM AFTER CYLINDER TEST = TRUE CONNECTION 31 OpenLPV I I I Evacuating for XX 32 — after EVAC Seconds Cycle X of X 32Close LPV I I Cycle X of X 33 — after VDLY 33 Open CGI I I I Filling forXX 34 — after FILL Seconds Cycle X of X 34 Close CGI I I Cycle X of X 31— after VDLY and LOOP < CYCLE 35 — after VDLY and LOOP = CYCLE 35 OpenLPV I I I Evacuating Manifold 36 — after VENT and VACUUM for XXX secondsTEST = TRUE 36 Close LPV I I 37 — after VDLY 37 Close VGS and CBVCANISTER CHANGE COMPLETE!!

Another embodiment of a bulk refill system according to the presentinvention is illustrated in FIG. 34. This embodiment illustrates onepossible configuration for employing a bulk refill system in a NovellusSigma Six unit. In this embodiment, a refillable ampule 30 as describedin connection with FIG. 8 is used. However, instead of employing twodigital level sensor assemblies 21, a single digital level sensorassembly 21 capable of detecting at least four levels is employed. Thedigital outputs of trigger points of the digital level sensor 21corresponding to the “HIGH” and “HIGH—HIGH” levels are communicated tocontrol unit 240 via cable 247. Similarly, the digital outputs of thetrigger points of the “LOW” and “EMPTY” levels are communicated to lowlevel monitor 120 via cable 235. The empty alarm output from the lowlevel monitor circuit illustrated in FIG. 22 is then interfaced with theelectronics of the CVD processing equipment. This output informs the CVDequipment when the source chemical level within refillable ampule 30 hasreached the empty trigger point and prevents further fabrication untilampule 30 is refilled. Further, the N.O. output of the “LOW ALARM”circuit can also be interfaced with the “CONTAINER NEEDS REFILLING” LEDin control unit 240 if desired.

An alternative exists for the four level output sensor (21) output suchthat the low level monitor is not needed. All four levels are interfacedto the BRC-22A (40) and an N.C. output on the back of control unit 240is used to interface to the CVD system for the empty alarm. This can beused if a remote indicator is not needed.

The CVD processing equipment in this configuration has a separatemanifold 160 for refillable ampule 30. Manifold 160 includes a separatevalve in delivery line 332 for closing off the supply of TEOS or otherhigh purity source chemical to the CVD reaction chamber. In additionmanifold 160 includes separate valves from that of valve 337 for closingof the inert gas supply and vacuum supply through passage 331 to ampule30. Accordingly, the three manual isolation valves 336, 337, and 338will remain open at all times once the refillable ampule 30 is installedinto the system. The process for accomplishing a refill of ampule 30 inthis embodiment is described in connection with FIG. 1.

The manifold of this embodiment is identical to manifold 222 describedin connection with FIG. 30. Furthermore, bulk container inlet and outletvalves 264, 266 are also preferably pneumatic in this embodiment. Thepneumatically actuated valves in manifold 222 and on bulk container 220are controlled in the same manner in this embodiment as described inconnection with FIGS. 30 and 33.

FIG. 37 depicts an arrangement of a bulk container and an ampule 30 thatis presently preferred with some systems. The valves having the samenumber as the valves in FIG. 34 perform the same function as previouslydescribed. In addition, a degassing cylinder 350 and correspondingbypass valves 351 and 352.

A particularly preferred embodiment of a bulk refill system 218 will notbe described in connection with FIGS. 35 and 36. FIG. 35 is a schematicrepresentation of a multi-point auto-refill system 164 (“MARS”)according to the present invention. The MARS control system 164comprises a CPU 167, at least one refill cube 170 with its own CPU, acorresponding number of remote interfaces 172, and a bulk cube 162 againwith its own CPU. This system is particularly applicable to use with theNovellus Concept One and Concept Two CVD systems, which is a PECVD unit.

One embodiment of a bulk cube 174 is shown in FIG. 36. Bulk cube 174comprises a bulk container 20, purge manifold 22, distribution manifold174, and automatic purge controller 140 (not shown). Becausedistribution manifold 174 contains four distribution block valves 175disposed in parallel in refill lines 244, bulk container 220 can supplya high purity source chemical such as TEOS to four different refillableampules 30 within respective refill cubes 170.

In FIG. 36, the components of the manifold with the same number as themanifold 222 described in connection with the bulk refill systemsillustrated in FIGS. 30 and 34 perform the same function. Further,canister inlet and outlet valves 264, 266 are also preferablypneumatically actuated valves. Thus, although bulk container 220 wouldpreferably have a larger capacity than the bulk container 220 of theprevious embodiments, removal and replacement of bulk container 220would be accomplished in the same manner. Automatic purge controller 140functions, however, are completed by the CPU at the Bulk Cube and masterCPU so that a refill sequence is not initiated for any of the fourrefillable ampules 30 during the replacement of bulk container 220, orfor that matter after a “BULK EMPTY” signal is communicated from bulkcontainer 220.

When bulk container 220 is in need of replacement, the “BULK EMPTY”signal is communicated to the Refill Cube and the Master CPU 167. Afterreceiving the signal to start the container change, CPU 167automatically initiates the drain and purge cycle required before bulkcontainer 220 can be disconnected.

Distribution manifold 174 comprises a plurality of distribution blockvalves 175, four in the present embodiment. Each distribution blockvalve 175 includes a refill line isolation valve 176 and a purge valve177. Each refill line isolation valve 176 is disposed in a branch ofrefill line 244. Refill isolation valves 176 are preferably N.C.pneumatically actuated valves. When a valve 176 is closed, no sourcematerial can flow through the respective distribution block valve 175 toa refillable ampule 100 or modified ampule 200. Each purge valve 177communicates inert gas supply line 178 with the respective refill line244 branches via distribution block valve 175. The purge valves 177 arealso preferably N.C. pneumatically actuated valves. When these valvesare closed, inert gas in gas supply line 178 is prevented from enteringrefill line 244. On the other hand, when a purge valve 177 is opened,inert gas is allowed to flow through the respective refill line 244branch. In this manner, each individual refill line 244 can be purgedwithout disrupting the operation of other distribution valves 175 or theflow of source chemical therethrough.

Pneumatically actuated valves 176, 177 are controlled by CPU 167 to openand close at appropriate times. Or, if desired, manual toggle valves canbe mounted in the cabinet for local control.

The overall layout of the refill configuration for an individual ampule30 in the MARS system 164 is similar to that in FIG. 34. The only realdifference is the multiple port configuration in the cabinet, largerbulk canisters and an integrated control system that replaces the lowlevel monitor (120), BRC-22A (240) and automatic purge controller (140).

Refill cube 170 includes refillable ampule 30, control unit 40, and lowlevel monitor 120. The “HIGH”, “HIGH—HIGH”, “LOW” and “EMPTY” outputs ofthe digital level sensor assembly 21 in refillable ampule 30 arecommunicated to the refill cube and CPU 167. In this manner, CPU 167 canmonitor the status of a plurality of refillable ampules 30. When any oneof them are depleted, digital level sensor 21 will signal CPU 164. CPU167 will then initiate a refill cycle for that refillable ampule 30 uponreceipt of a system “idle” signal from the electronics of thecorresponding CVD reactor if available. If the signal is not available,a manual start would be required. This prevents the premature initiationof a refill cycle while the CVD unit is in the middle of processing abatch of wafers, which would result in the loss of the batch.

The status of refillable ampule 30 in each refill cube 170 iscommunicated through a remote interface 172 to the electronics of CVDunit. This is done so that the CVD unit does not initiate a run whenthere is insufficient source chemical in ampule 30 to complete the run.To ensure that the tool remains idle during the entire refill process,CPU 166 or low level monitor 120 will inhibit the user from initiatingthe wafer fabrication process by providing an ampule low alarm to theelectronics of the CVD unit. The ampule low alarm will not allow theuser to start any sequence until the alarm is removed. Once the refillcycle is complete and the refillable ampule 30 container re-pressurized,the alarm will be removed so that the process can be started.

The MARS system of the present invention offers benefits in systemavailability and process stability. The automatic refill configurationallows for 100% availability of the process tool and eliminates thedowntime associated with the more frequent changeovers required with thesmaller bulk containers 20. In addition, complications that can arisefrom a container change, which can further extend the downtime of theprocess tool and require additional resources before the system can beturned over to production, are minimized. Those complications aretypically: process requalification for deposition rate, uniformity andparticles, liquid injector and liquid flow controller (LFC) malfunctionsand replacement, or other delivery related problems.

The MARS system and the refill configurations disclosed in FIGS. 34 and37 have another benefit that results from the transfer of chemical fromthe bulk container in a remote area to the refillable ampule in the fabarea. This added benefit is that is a reduced amount of dissolvedpressurization gas. Thus, the transfer performs a de-gassing function.The TEOS or other high purity chemical transferred from bulk container20 is degassed upon transfer to refillable ampule 30, because refillablecontainer 30 is under vacuum prior to transfer. When the refill starts,the TEOS or other high purity source chemical passes through thecritical orifice of the valve on the recipient container 30 and isexposed to a significant pressure drop. That pressure drop results incavitation of the liquid which results in a significant reduction ofdissolved gases in the liquid chemical. The amount of dissolved gas (Heor Nitrogen) in the liquid is significant since that gas will come outof solution and cause LFC instabilities and wafer inconsistencies.

The benefits of the MARS system and the corresponding hardware alsoinclude:

1. A refill system with a much higher level of intelligence. There areseveral microprocessors being used to monitor various inputs and theprovide corresponding outputs. Processors are resident in the CPU 167,Refill Cube 170 and bulk cube 172.

2. The MARS system can integrate the function of all controllerspreviously used. That includes: the control unit 240, the automaticpurge controller 140, and low level monitor 120.

3. A large number of refill points, bulk cabinets and system statusinterfaces can be monitored using one control system.

Although the invention has been described in connection with referenceto preferred embodiments and specific examples, it will readilyunderstood by those skilled in the art that many modifications andadaptions of the inventions described herein are possible withoutdeparture from the spirit and scope of the inventions as claimedhereafter.

We claim:
 1. A canister for a chemical delivery system for high puritychemicals, comprising: a metallic container comprising an inlet and anoutlet; an inlet pneumatic valve integral with said inlet; an outletpneumatic valve integral with the outlet, wherein said pneumatic valveintegral with said inlet and said pneumatic valve integral with theoutlet are constructed and arranged for removable attachment of thecontainer to a delivery manifold for dispensing high purity chemicalmaterial from the container through said pneumatic valves to thedelivery manifold, wherein said pneumatic valve integral with said inletand said pneumatic valve integral with the outlet are attached directlyto the container without any manual valves, so that when the containeris removed from the delivery manifold, the pneumatic valve integral withsaid inlet and the pneumatic valve integral with the outlet remainstructurally integral with the container to isolate the interior volumeof the container from the surrounding environment, and wherein saidoutlet pneumatic valve is coupled to a dip tube; and a level sensordisposed within the container.
 2. The canister of claim 1, wherein theinterior of the container is made from electropolished stainless steel.3. The canister of claim 1, wherein the container includes a levelsensor in the container, wherein the level sensor is a float comprisinga float and a shaft upon which the float is slidably mounted, andwherein the float sensor has at least one trigger point.
 4. The canisterof claim 1, wherein the container includes a level sensor in thecontainer, wherein the level sensor is a metallic float sensorcomprising a metallic float and a metallic shaft upon which the metallicfloat is slidably mounted, and wherein the metallic float sensor has atleast one trigger point.
 5. The canister of claim 1, wherein thecontainer includes a level sensor in the container, wherein the levelsensor is a capacitance probe.
 6. The canister of claim 1, wherein thecontainer includes a level sensor in the container, wherein the levelsensor is an optical sensor.
 7. The canister of claim 1, wherein thecontainer includes a level sensor in the container, wherein the levelsensor is digital.
 8. The canister of claim 1, wherein the containercontains a chemical having an overall purity of at least 99.99%.
 9. Thecanister of claim 1, wherein the inlet valve and outlet valve arenormally closed pneumatic valves.
 10. The canister of claim 1, whereinthe outlet includes a metallic tube disposed in the container.
 11. Thecanister of claim 1, wherein the container includes a level sensor inthe container, wherein the level sensor has at least one low leveltrigger point.
 12. The canister of claim 1, wherein the inlet valve hasan inlet port.
 13. The canister of claim 1, wherein the inlet valve hasan inlet port, and wherein the inlet port includes having an attachmentmeans for removably attaching said inlet port to a chemical deliverysystem.
 14. The canister of claim 1, wherein the inlet valve integralwith the inlet is a normally closed pneumatic valve, wherein the inletpneumatic valve comprises an inlet port, wherein the inlet port has anattachment means for removably attaching the inlet port to a chemicaldelivery system; wherein the outlet valve integral with the outlet is anormally closed outlet pneumatic valve; wherein the container includes alevel sensor in the container and wherein the level sensor comprises acable for providing a low level control signal to a low level indicatorcircuit to indicate the level of high purity chemical in the container,wherein the outlet further comprises a metallic tube disposed in thecontainer from the integral outlet pneumatic valve to a point below thelow level sensor trigger point.